[gigel82]

Didn't do a deep dive, but it looks like they have distributed data structures (DDSes) on that layer, which appear different to CRDTs (merging on the client, not on the server).

I can imagine someone could build a multiplayer game on this thing (though I doubt that's what MS designed for).

[WorldMaker]

From what I recall of a BUILD talk once on the deep dive fundamentals, Fluid is based on CRDTs under the hood (or possibly the CRDT predecessor OT like Wave was), but Fluid believes writing CRDTs is hard (it is), especially writing them that obey the math laws CRDTs are supposed to, and then getting that to perform well (including and especially things like catch-up/replay) is also hard, so yes the actual programming interface Fluid presents is high level "distributed data structures" though the wire format is closer to CRDTs with some cheats from assumed knowledge of the data structures (things like sending the latest contents of a list for catch-up rather than replaying the entire CRDT chain for that list).