I don't actually know the answer to to that because I don't know the exact mechanism of transferring the launch command, but that sounds like it would make sense. You are right, it is impossible to guarantee the same coordinates - this method depends on the two missiles behaving the same way on both clients. It all works fine _most_ of the time, but it would be nice if guided missiles (I suspect unguided rockets aren't as big a deal and given that MLRSs and other entities can put a LOT of those in the virtual air ... ) would be synced every second or five to ensure they're on track in both simulations.
I have seen significant desync even with a low number of players - it's rare, but very obvious when it happens. Guidance improvements can actually alleviate a bunch of it because it will smooth out missile reactions at longer ranges, but this is only one part of the puzzle as things happen as shorter ranges also.
Doesn’t that mean that the more clients that are present, the more likely it is that different sets of data with lag/latency and jitter will be formed and interpreted? It sounds like it would be impossible for one missile to guarantee the same coordinates are output as each client has different network properties and behaviours!
