Personally... if AmigaOS4 includes a 68k emulation engine for backwards compatability, I don't see the problem.
Looking at MacOS8, and also 7.5+ they included an 68k emulation engine, so the software not yet ported to PPC would retain functionality. And again, with OSX86, they included a PPC-emulation engine (rosetta stone) so that PPC-compiled software, where still functional.
Now, IF AOS4 have that 68k Emulation engine ("classic engine" might be a suitable name?) there's no point in arguing about whether or not the PPC is an "amiga CPU" or not. C= themselves was developing (or trying to develope) a PPC Amiga just before they went bust.
So for ME, a PPC Amiga, IS an Amiga, as it's been "official" since before C= went under