Grant Hill explained the thought process that went into Team USA selection.
In an interview with Andscape's Marc J. Spears, Hill shared a great quote when asked about the challenges of assembling a 12-man roster from such a strong talent pool.
"It's like a puzzle, man," Hill told Spears. "You got to put the pieces together that fit and that complement. And so, as a result, you are leaving guys off who are really good and guys that I?m a fan of.
"... But a coach once told me that a team is like a piano recital. You got piano movers, You got piano tuners, and you got piano players. And you need all three to put on a good show. You can?t have all piano players. And so that may fit this or may not, but you need roles and you need guys that fit."
https://www.nbcsportsboston.com/nba/boston-celtics/grant-hill-derrick-white-team-usa-olympics-roster/628345/
Hill heaped praise on White?s fit.
?One of the many things that I really love about Derrick, and particularly with this team, is I don't feel like his role changes much with our team, from what he does with the Celtics,? said Hill. ?He plays alongside two incredibly great young players in Jaylen Brown and Jayson Tatum.
?This setting is hard when you come in and you have to sort of -- you're the center of your universe and now you have to establish a role and might be different than what you have to do with your team. And so to have someone who can come in and play off of guys, be complementary to some others, but then also stand out and be a dynamite defensive player and knock down shots -- just impact winning.?
https://sports.yahoo.com/grant-hill-explains-why-team-025257908.html
Reading between the lines they probably thought that Jaylen would have wanted to be one of "the guys". Like if you look at this year's ASG, he took the 2nd most shots of anyone on the East team:

Then you look at 2023 ASG, he took the most shots and had the most points on Team LeBum:

I won't link to the 2021 ASG but it was the same deal. Looks like they didn't plan to play Kawhi a lot due to his injury anyway, and when he withdrew they wanted a glue guy and they didn't think Jaylen could play the role of a glue guy. That's my guess on what happened.
Mind you I think they should have picked him ahead of Booker. Now if KD has to withdraw, I think that Jaylen should definitely be a more solid fit if they want to replace a guy that's going to be a cornerstone with another cornerstone. I would definitely be thinking something sketchy's going on if he doesn't get picked in that instance.