Hi, I Just bought a 2020 1500 Classic with the Sub-zero package and I’m having a similar experience. Either there is something wrong with the heated seats or they are just pathetic. On high they never really get hot enough that we have to turn them down to low. It also doesn’t feel like the heating pad goes all the way to the front of the seat, or very far up the back.
I am comparing them to a 2009 Elantra and a 2016 Camry. Both of those vehicles seats heated up quickly and got warm enough that you had to turn them down at some point.
I have only had the truck a few weeks, and thanks to Covid I’m not in a hurry to take it in just for the seats.