I just can't see Apple going all out to try and hobble the cMPs from the new OS for the simple reason as ask yourself, "What is the profit in it for them?" If you think they're driven by the notion if the cMP is retarded in this way then all, most, or even many of these users will abandon them and rush out and by a nMP, you're mistaken. I think everyone on here and Apple knows that is just not going to happen.
Look at Apple's price point for the nMP as well as the comments on this forum and the Facebook group. People using cMPs are gagging, likely from envy because, they like me, see the righteousness and beauty in the engineering, design and functionality, but, they, and again, like me, just can't afford it. Suddenly making their cMP stuck in time OS wise won't make them, or me, suddenly able to afford a nMP. The nMP is not aimed at the mass market or even the enthusiast crowd, it is for the highest use production environment - scientists, video & audio production and photography where IT MUST WORK, and IT CAN NEVER GO DOWN are daily mantras. Those environments won't tolerate a piece of capital equipment (which is a Mac Pro) being held together with duct tape, rubber bands and baling wire subject to usability and reliability caveats and instability.
To date everybody (both the enthusiast and production crowds) have had to do with the cMP because it was much more versatile and equally or more powerful than the trashcan. It was a plus that the enthusiast crowd could get onboard at an affordable price point. But Apple is leaving them behind with the nMP and playing whack-a-mole with us on here to keep from enjoying Catalina (and then only somewhat, considering functionality that just won't work on older hardware) is not worth its time or effort because they won't convert an appreciable number to the nMP (although maybe a tricked out mini + eGPU & external storage). If people want to hack the system to get it to work and suffer the limitations in functionality as well as instability, Apple, as a company, is more likely than not, unconcerned.