When our 2022 Denali was new there were a couple of times when something unusual happened with the brake pedal. It might be what you describe but I am having trouble remembering exactly what it did. I think after driving, then stopping, going to park, setting the parking brake, and turning off the engine it would happen. I think then stepping on the brake it would move more than usual along with a whooshing sound. Very strange and unexpected. I think that I simply stopped messing with the brake pedal after I was stopped and have not had it happen for quite some time. As far as what the Dealer says, go to another Dealer and talk with someone else. Remember you can go to Chevy and Cadillac Dealers as well.
