Note that he says that Commodore, they _tried_, not that they succeeded.
AROS will make it.
Gemini was more a test bed for the rev 8 buster. I don't think it was ever designed to be turned into a product.
I think it worked as far as they went. Trying to make two separate CPU boards operate as a single Amiga is hard though, much harder than using multiple cores on a single modern cpu.