Tl;dr stop spreading FUD.
I have three different pkgbase BEs on a single machine, 14.3-S 15-S and 15-R:
- started from 14.3-R;
- converted to pkgbase;
- created a new BE and upgraded to 15-R;
- created a new BE and upgraded to 15-S;
- went back to 14.3-R (because 15 doesn't resume from suspend reliably on my machine);
- upgraded to 14.3-S.
All this using pkgbase without compiling the base system a single time. Not only that, I move from one BE to another every few days to check it the development progress on 15 is going on for my problem and with pkgbase I can choose which BE to update.
You clearly don't know what you're talking about, and BTW is not the first time that this happens. Just stop, thank you.