EM likes to reexamine things through the prism of "first principles." Mass, velocity, time, that sort of thing. It lets him see problems from a new perspective, rip up old, traditional techniques, and apply brand new ones that promise to be better, faster, more efficient.
But, if "Does it work?" isn't a first-principles issue in manufacturing, I'm not sure what else is. And plainly, the phone-as-key did not work as intended (seamlessly, flawlessly, for everyone no matter the platform, and always). Which, when you think about it, describes a fob pretty well.
If he's looking at the phone-as-key problem through that first principles prism, EM really has no choice but to address it. That said, it's still to his credit that he's willing to step back from his (substantial) ego, admit there's a problem he (partially? entirely?) created, and apply the engineering horsepower needed to fix it once and for all.
Robin