I'm not the down-voters, but my guess is due to citing the 1-in-a-million figure, which is Apple's claim about a random false positive, in response to a question about false positives with twins. Someone reading fast or simply not thinking critically could come away with the wrong impression.
He got downvoted because he said something that didn't match up with what OP said. In the presentation, Apple said
> The probability of a false match is different for twins and siblings that look like you
So that means the 1 in a 1,000,000 chance doesn't make sense here because Apple said the probability is different in regards to twins and siblings that look like you. So @gre just spouted off the statistic when OP was asking what the probability might be in regards to twins and siblings, because Apple says that it is different.
Re:FaceID Security [pdf]
by matthewmacleod on Wednesday September 27, 2017 @02:26PM
(#15350772)
They did, but the quote above was about confusion between twins or siblings. Those are explicitly not random people.
As far as I remember, in the big reveal, they did make a point of saying that faceid had a much lower chance of of colliding than the fingerprintid system.