Tell you the truth, that doesn't help clarify to me much.
If it is compatible, then can't I 'drop it in'.
They sound like they are saying the same thing.
It is compatible so clients can connect to the server and be fully operational, and thus, I should be able to drop in this server, and use it as a server?
How can it be compatible if it doesn't maintain data, configuration, etc..
Edit:
or is this about Pumpkin files. Pumpkin will maintain it's own files, data, configuration. So it can't just use existing Minecraft data files.
So if it was a new world, Pumpkin would generate new pumpkin formatted files. But couldn't just 'drop it in' on an existing world and use the existing Minecraft data files.
Not sure of long term viability as far as effort, but if it is files, couldn't a converter from MineCraft to Pumpkin file structure, make the server 'drop in'?