I finally understood the AOS 4 point.
They think that Amiga OS must run on original HW designed for it. That's what made Amiga what it was back in the late 80's.
It might be a "sacrilege" running Amiga OS on an "OLD" hardware. Even if the newly designed HW is less powerful and cost 3x times a dual liquid-cooled G5 Power Mac.
They probably know that just a small group of people will pay a lot of money for the new HW. But maybe the difference in revenue for including support for old macs it's not worth going against their principles...
Those are just my 0.001 cents!

Rgds,