We have cross-field invariants that merging at the data structure level can't ensure (in an obvious way, at least), and "lose the semantic meaning of a conflict". The main idea behind their approach is that certain parts of the model can have custom "mergers" that are able to run business logic to maintain these invariants.

Worth noting, the decision to eschew CRDTs predates my time here, and I've pushed for a CRDT rewrite quite a bit since I believe it could be done. The other main concern they had was memory usage, but it seems like EG Walker would solve that. Our system uses a "Commit DAG", (an Event DAG by another name), and does a three-way merge using a common ancestor of the diverged documents, and so a lot of the bones of EG Walker are there, and I'm exploring ways in which we could gradually move to it.