The iPhone isn't a Mac or a PC. In fact, iPhones work on both, so even if PC Guy was, literally, a human PC with the Windows running in the background, he'd still be able to use the iPhone.
but it's not. It might be kind of ironic if his character used an iPhone, although not that ironic since iPhones are PC compatible. But it's not ironic at all for an Apple spokesperson to be using an Apple product.