Whatever CYA decision they came too, it's obvious the 3rd base ump thought foul ball. He basically gives up on the play and isn't watching anything until he realizes the kid is running to 3rd. Even then, you can almost see the "WTF, I better look official here" postureIf you watch the process of the replay, they confirm the call on the field of fair ball. There has been plenty of debate on many other aspects of this.
I find it hard to believe, but not impossible, that he verbalized “Fair!” However, his body language and reaction AFTER his call does not indicate “I thought it was fair but goofed.”
I don't know the mechanics. Which ump would be responsible for watching the ball into the OF? If he thought fair, he didn't even glance into the OF. Is that the 2B umps job?