Sorry to spoil it for you, but…
It seems that some people think that Face ID failed during the keynote, but what actually happened there – I think – was that Craig picked up the wrong iPhone. One without Face ID setup for him. This is why it showed this: “Swipe up to unlock” and “Your passcode is required to enable Face ID” after
two five attempts. Note the “to enable Face ID“. As in. It was not setup for him.
Well. So far for the failure during the keynote.
Edit: Actually. Looking at the facts. This doesn’t look good for Apple. Certainly not for a GM.
Edit-2: Well. maybe not. I checked the keynote once more and it seems that Craig looked at the iPhone X twice before Face ID got disabled. He didn’t even notice it.
The first time Craig didn’t pick up the iPhone, but he looked at it on the table. This was attempt number one. And it failed to recognise him.
The second time Craig did pick up the iPhone, and he looked at the iPhone, but only briefly. This was attempt number two. Which also fail to recognise him.
After this, Face ID was disabled, because that is what it should do. Disable Face ID after
two five unsuccessful attempts.
Ergo. The problem was that he looked at the iPhone X, but not long enough.
Edit-3: The problem appears to be even simpler. Well. According to Apple that is, because their explanation to David Pogue was this:
“People were handling the device for stage demo ahead of time,” says a rep, “and didn’t realize Face ID was trying to authenticate their face. After failing a number of times, because they weren’t Craig, the iPhone did what it was designed to do, which was to require his passcode.” In other words, “Face ID worked as it was designed to.”
Ok then please, please explain to me why Face ID on the backup iPhone X worked. Let me guess. That iPhone X wasn’t handled by the same person, but Craig himself?