It's the only way to do certain things but the devx is burdensome. It might be easy enough to do a thing but the major issue is that you have to constantly fight wonky behavior when working in a team.

If someone adds a new submodule, you need to know to pull it or at least init it. You need to know the code is in a submodule and treat it differently, complicating integration procedures.

It certainly does not behave the same in that you certainly can't ignore whether it exists once it's set up.