That's not a fragmentation issue like you're suggesting it is, people suggest that there's some sort of fragmentation problem, but Google has that figured out and the only people that are harmed by it are people who bought early Android phones and ones with custom UI. Pretty much all the newer ones should be easily handled by somebody with the technical skills that John has.
How many Android phones do not have a custom UI? Or are you not referring to things like TouchWiz, MOTOBLUR, and Sense? Also, for every big android phone of the month like EVO, Galaxy S, Nexus One, G2, or Nexus S, there are at least 20 new phones with near minimum specs and Android 1.6 or 2.1 if you are lucky. Don't get me wrong, I love my EVO, but with graphically intensive games it helps to have less hardware and software differences to compensate for. If they only target, say, phones with Froyo and 1 Ghz or faster processor, they are limited to Nexus One, EVO, Droid X, Droid 2, G2, and maybe a few others(IIRC the US Galaxy S phones do not have 2.2 yet, but the European models do).