> And because Electric syncs every change granularly, you are certain that the state of your local database is exactly the same as the server's.

I don't see how this certainty follows from "granularity" (whatever that means in this context). I believe to have such a certainty one would need the synchronization to happen within a single transaction that spans both client and server databases.

Correct - granular syncing alone doesn't guarantee consistency; you'd need either a distributed transaction protocol or a conflict resolution strategy with eventual consistency semantics.