I mean, they aren't perfect, but you've got to admit they were solving a hard problem with immense technical constraints. And they certainly care about robust synchronization, since subpar netcode can absolutely determine the success or failure of certain types of games (shooters, fighting games). Players always whine about netcode all the time, although 100% byzantine fault tolerance is not the goal.

Speaking of which, do you really need byzantine fault tolerance in a document editor? I mean, it would be really great if it were possible, but given the vast number of different operations you can perform in a document it seems like a really daunting task to do so both formally and practically. And Google Docs isn't really comparable to Bitcoin or airplane control systems anyway. Perhaps temporary periodic backups (like saving diffs to documents in 5-second intervals for a recent period window, so you can rollback if things seriously fuck up) as an escape hatch would be good enough?