Yes i have a 2020 sierra at 40k miles and I've noticed the same thing after the first 10k. I've taken it to the dealership and only managed to convince them to look at it since i bought the platinum warranty. They serviced my seat and it is still uncomfortable with the rumble bars digging into my thighs.
Edit- I also noticed that the passenger seating is so much more comfortable. One of my coworkers even commented that it was like sitting in a recliner. It's very frustrating the lack of support from gm on this issue and knowing that if every alert package didn't require these rumble strips the seats would be way more comfortable.
