I'd disagree they are naive. These all stem from my team's experiences developing platforms at a large international bank.
We have dozens of packages that share many of the same dependencies, moving those to a single copy of each would reduce used disk space by equal dozens of times. But saving disk space is almost more of a nice side effect of the other solutions.
We've tried reducing this by using lerna but that can only go so far due to only supporting a single shared version or fully independent versioning. Hence the more customisable workspaces.
I'd also contend this is not a narrow use case, every bank in London is building similar platforms and could benefit from something like this. They just tend to not talk too publicly about what they are doing.
I haven't, but had a chat with Zoltan on twitter (a dev on it). It does seem to be pretty good, and definitely would be a less drastic solution since it builds on top npm.
It honestly reads more like a classic case of “My very narrow use case is the general case”. A common mistake.