I’ve had 2 BMW low seats, the first was on my 2012 GS and the second is on my 2015 GS. I find them fine, and no numb bum.
I bought a air something or other for a trip to the Picos, but took it off before I got there as I found it uncomfortable. On the way back I rode over 700 miles just with the low seat on in one day, with temperatures ranging from 20 C to the lower 40s C. I got home at 11 at night, absolutely knacked, but no sore bum.