I have been a professional Mac developer and consultant for many years now and can’t agree that it is mainly about not wanting to test on older machines.
I was working on an iPad app for pilots of private jets, several years ago, when the 64bit bombshell landed and we were suddenly faced with the need to recompile 32bit cross-platform code written for the FreePascal compiler, which had not then been updated to 64 bit and was out of our control.
So there can come a time when it is no longer feasible to keep old code going due to having to introduce a whole slew of
#ifdef … #endif statements to cope with both platforms.
Fortunately, we were able to keep going for a while but when 64bit became mandatory, the project had to come to en end.
The reality is that it is really difficult for a developer to work on new stuff, made possible by new APIs, always looking over their shoulder to see what they have to leave out of the version that is meant to run on the legacy system because the “latest and greatest” feature that customers have been screaming for simply isn’t possible without the latest APIs.
I would think that the computational power required for features like DeepPRIME would be very difficult to achieve on a 32bit architecture.
Nonetheless, it still hurts having to upgrade a computer, just to run the latest version of the OS