This is a solid point, but iPad workloads were pretty clearly converging with laptop workflows. (And Apple was obviously moving in the direction of converging the SDKs even before the M1 was announced.) Plus, they already had the ability for devs to build apps to run on MacOS & iPad/iPhone. This was a strategic move that was visibly underway for years.

> a successful transition was entirely dependant on how well rosetta works (it turns out it works well, but that wasn't a given at all), evidenced by how people got burned in the powerpc-x86 transition

All the more reason to expect them to make a transition -- they had pulled it off successfully (if with some hiccups) before. I would not be surprised if they had some of the original Rosetta team around to revise for this time around.