Heard mine do that on any incline as well. Think it’s just the sound of the trans coming out of park. If you ever tried taking a car out of park on a hill when you had to pull on the lever and the lever was actually physically connected to the transmission linkage underneath, it was harder to pull the lever when you were parked on a hill because of what was called (IIRC) torque lock, and when you finally pulled hard enough to get it out of park it made a loud snapping sound.
These shift knobs are all electronic so all you’re doing is sending a command to the transmission to actuate the shift linkage into the correct position and whatnot, but you’re not physically moving the linkage yourself, so there’s a small delay between selecting a gear on the dial and the linkages down below actually moving into position. You’re hearing the sound of the transmission coming out of park with the extra pressure of being parked on the hill.
When you park on a hill, apply your parking brake and shift into neutral, take your foot off the brake and let the car come to rest on the parking brake, THEN shift into park. This puts the load of being parked on a hill on the parking brake and NOT on the transmission, and then it will come out of park easier and quieter.