Just to clarify, I meant that it is natural for the masters. Slaves are perfectly fine with input-only behavior. Obviously, it i better to get it documented, since it would allow parallel operation like it required here.
In this case, it looks like for programming operations you have to introduce delays yourself. The page programming takes 20 ms, and there are no status bits for that. Erase also takes 20 ms, but there is a status bit. Not sure if device would allow reading of that bit wile operation is ongoing though.
I have boards on a way SLG46824, we'll see how all that works.