I could be wrong, but I think the hvac system comes on at nearly full strength when the car is remotely started and settles into the last setting once you either open the door or push the ignition button. I usually leave my on auto and the fan is much higher when i first open the door than it would be if I started the car normally (not with remote start). There are also some settings in the menu you can adjust on how the system works when started remotely.
My 2019 Blazer does not come on full blast when I use the remote start no matter what setting I leave it on. I have it on max yet at 30 below I have to go out and start the vehicle manually. I heard the remote start works the way it should in the 2021 Blazer. Just trying to confirm this. Thanks.