The ideal case isn't running OS X, it's for (Apple to allow) Windows (or Linux) to output OS X builds. Switching to OS X doesn't solve that. A quick read of Apple's license would imply that's prohibited, thus it's a clever bit of rules lawyering to suss out that Apple's license doesn't require that their software be running on bare-metal on OS X, just Apple hardware. This means it's possible to output OS X builds while not running OS X, in limited cases with the proper configuration.