Him wanting off the team is pure, unsubstantiated conjecture.
What Booker said, without going back to find the exact quote, is that he doesn't want to continue missing the playoffs.
Miss the playoffs? How about not getting blown out every game. Would you not react?
Put yourself in his place. He's an intelligent young man, NBA basketball is pretty transparent and he sees the writing on the wall.
Remember when Sarver (I think it was he rather than McDonough, but either way) announced that Devin would be involved in player personnel decisions?
I wouldn't bet the ranch that they honored that. And now they've added a coach who has been caught lying to the Press to cover up his inadequacies.
And it just gets worse and worse.
P.S.: Your using the word "wanting" is present tense. No one said it's going to happen now. But he's beginning to show signs. It makes no sense to overlook it.