In his first interview since Facebook’s (FB) IPO, CEO Mark Zuckerberg reiterated once again at TechCrunch Disrupt that the social network is not building a smartphone to compete directly with Apple’s (AAPL) iPhone and Google’s (GOOG) large assortment of Android devices. Echoing what he said in a July earnings call, Zuckerberg remained firm that a Facebook phone “just doesn’t make any sense” and that even if it was considering a bid to enter the mobile hardware market, it would probably only manage to attract “maybe 10 or 15 million people to use it.” Zuckerberg told TechCrunch that Facebook will double down on mobile by having direct system-wide integration a la iOS 6 or improving optimization for its apps by switching from HTML5 to native code.