I think that particular design was plagued with efficiency problems, besides being too far ahead of its time (the software was purportedly quite advanced and likely prohibitively expensive).
Jetoptera are saying they get a 10% improvement in propulsive efficiency with 50% of the fuel consumption ... I have a lot of questions ... 10% at what ratio? across the board? on average? Does that combine with the 100% fuel efficiency increase to get 110% more thrust for the energy consumed?
Why can’t they run this device on an edf? (There is some mention of needing batteries abt 1500Wh/kg?) Those are well known for being horribly inefficient, and I’d imagine getting a 110% efficiency boost for even a model edf would be making waves all around in the modeling community.
Lastly, there are all sorts of interesting edf quadcopters; see, for example: https://m.youtube.com/watch?v=5L6FSdUmEpg It seems like it should be trivial to apply this tech to a prototype of that scale and demonstrate its effectiveness, but as the article points out, it seems most of the prototypes are for fixed wing aircraft. Why not just go right to vtol prototypes?
I do not know whether this is the case here, but the trick to making such claims, without actually dissembling, is to first be highly specific about what it is that you are measuring and comparing, but then be quite vague about it in the press release, trusting that a journalist will cherry-pick from the claims to make his story look exciting, and quite possibly mix and match claims that cannot be satisfied together.
If this technology really could give 10% more thrust with half the power and 70% of the weight of a turbofan, then Jetoptera (or some other company) could be making real money converting at least business and commuter jets to use these devices - so why isn't this happening? The whole 737 MAX debacle started with Boeing being under intense competitive pressure to improve fuel consumption by just a few percent.
We also see that "Jetoptera is more or less agnostic about where it gets its compressed air from, although it reasons battery technology will need to reach energy density figures around 1,500 Wh/kg (current state-of-the-art batteries are around 260 Wh/kg) before it'll start making sense to fit the J-2000 with an electric compressor." That would be just a 477% improvement in a feld where 10% is a big deal! Note that current battery technology is already sufficient for conventional electric airplanes to begin to be useful.
With regard to your last paragraph, none of these technologies are trivial even in isolation, let alone combined, regardless of the number of puff-pieces like this one written by people whose enthusiasm seems to exceed their understanding.
You're dead on the money about making claims that are very precise, and then leaving the door open for the media to generalize them to make headlines.
In this case, it may well be vaporware, but it's also possible it outperforms conventional aircraft in a way that's not particularly useful to consumers (small lifting capacity, high acceleration profiles, simple landing/takeoff requirements, etc) but might be useful for drones or military applications.
Yeah, turbojets are VERY inefficient on fuel, so that is a low bar.
Compare this to ships like the V22 which have an immensely complicated gear, shaft, and clutch arrangement to drive the props; this one also folds. Or against most multi rotors including the original Moller design where you need at least 8 engines or motors, two at each corner for safety, where you need a smart computer to balance the loads as motors fail.
Also as you just need pressurized Gass in the manifold for the thing to fly I wonder if an emergency system with a pressure bottle or even gas generator could be used to give you say 30 seconds of flight time needed for safe emergency landing if your pressure generating engine fails.
Not to mention making it easier to combine two or more independent engines to feed the manifold for redundancy without the crazy complicated and heavy gearing V22 has to achieve that, as mention above.
Although with only 4 ducts you might expect that problem space to be solved.
 - https://www.youtube.com/watch?v=bPZI6XoHi10
 - https://www.youtube.com/watch?v=A7NVgKrrxgI
Not those dumb things with WHEELS. The actual skateboard (sans wheels) hovering a couple inches off the ground.
I’ve always wanted one and at 33, looks like I’m gonna have to be the one to do research and development in this area (should my side projects come to fruition and net me the startup capital).
That's a bigger problem than the propulsion.
But yeah, it kinda cheated by starting the glide very very high & fast.
But it doesn’t solve the problem that VTOL aircraft like this are fundamentally unsafe, as they lack the ability to glide effectively and they don’t have the option to autorotate should the propulsion system fail. Helicopters are already significantly less safe than airplanes, and VTOL aircraft tend to be less safe still.
Even the Harrier, which at least could fly normally, was notoriously crash prone, with an accident rate 3x higher than the contemporary F/A-18. The V-22 is proving to be a pretty reliable marine killer in its own right, and that’s before you account for its abysmal uptime and tendency to be grounded.
Perhaps this aircraft will fix some of the issues of past VTOL aircraft, but I’d still be super wary about getting in one.
But most designs have at least some lift, which means there is some optimal glide ratio that minimizes vertical speed. Finally, having separate, isolated systems helps as well. This is also common with multi engine aircraft where an all engines out scenario is very rare. It's a challenge but not necessarily something that can't be addressed. Even some simple airbags could help here.
Autorotation only works if the rotor system has significant rotational inertia and a cyclic (blade pitch) control. Most powered lift designs have multiple small, low-inertia fixed-pitch rotors. If you lose power you're going straight down and probably tumbling out of control.
Airbags can help a little in some low-altitude crash scenarios but if the aircraft is falling out of control then there's no way to guarantee that the airbag will be oriented the right way. It's just not practical to cover an entire aircraft in airbags like NASA did on the Pathfinder Mars landing: the technology doesn't scale up.
The Osprey has a really nasty habit of doing this. A number of them have crash landed upside down from relatively low altitudes, which is a very bad thing.
Previous attempts/prototypes haven’t been super successful
And a whole plane with a similar system of air being ducted through the surfaces and whatnot