Considering how little effort it would take to make PS3 versions of their controllers, if Min-Liang's not doing so because of some kind of personal preference for Xbox, ignoring the obvious market, and free money... well... he's an idiot.
And, I'm going to go with the assumption that someone who's built his own successful gaming accessories company wouldn't be purposefully doing something so insanely stupid... which leads to the obvious logical conclusion:
Microsoft is greasing his palms somehow.