I‘ve heard register windows are more common in embedded
Depending on how liberally you want to define 'register windows', particularly if you include "two register sets", one could certainly say this is true. Many architectures have dual register sets, usually touted as for "fast interrupt handling" or other optimization based on not having to save the whole register file. Even the venerable Z80 has something like this. I have always assumed that's where the original idea grew from: if being able to speed things up by not push/pop-ing the registers is good for one type of context change, why not all/more of them?
I'm not enough of a theoretician or pedant to augur where register windows begin or end, however.