> Be a drop-in replacement for vanilla or other servers
It seems to me that unless it's a drop-in replacement its not a Minecraft server? Akin to how say an Uno deck isn't a drop-in replacement for a Hearts deck but still both card games but not both Uno decks.
Or is it just meaning that Pumpkin (besides the network) do things differently than vanilla and so you might not be able to open a vanilla created world using Pumpkin?
The common problem with Minecraft server implementations is that they are not bug-for-bug compatible, which will lead to certain techniques (especially redstone contraptions) breaking. The technical Minecraft community depends on many implementation details which not all servers support
I edited in scare quotes for "complete" to make that clearer, but I mean in terms of at least having matching blocks/mobs despite many differing details.
There are issues other than not ported bugs. Redstone in bedrock is know to be unreliable.
For example, in Java version if you take a circuit and activate it with a button/lever - it would always behave in the same way. In bedrock same setup could have random result. And "random" is something you don't want in a large sophisticated contraption.
I'd guess it's caused by some race-conditions in bedrock implementation, but alas it wasn't fixed in 7 years.
Minecraft has a lot of bugs or otherwise surprising behaviours that parts of the community have come to rely upon. This means that most non-vanilla minecraft servers aren't 100% drop in replacements. You have to make a decision what behaviours you want vs the performance and simplicity gains you will gain.
For example there there are tricks that allow you to delete bedrock blocks. Which then lets you either get onto the roof of the nether, or drop below the bottom of the world. Not all of these tricks will then work depending upon the specific minecraft server.
Another example is that in vanilla you can "bomb" people with experience orbs, the sheer number of orbs on the screen will grind their game to a halt since there are too many objects to track and render. Some minecraft servers work around this by grouping up experience orbs into a single bigger orb. That way you have fewer orbs on screen at once.
One bug abuse that blew my mind recently is the ability to have wireless redstone in vanilla [1]. I fell deep into that rabbit hole after a previous post on here about Bad Apple in Minecraft [2].
> Be a drop-in replacement for vanilla or other servers
It seems to me that unless it's a drop-in replacement its not a Minecraft server? Akin to how say an Uno deck isn't a drop-in replacement for a Hearts deck but still both card games but not both Uno decks.
Or is it just meaning that Pumpkin (besides the network) do things differently than vanilla and so you might not be able to open a vanilla created world using Pumpkin?