I can tell you that the seat heaters in my 2008 C2S are quite weak compared to the seat heaters in our Mercedes and BMW. So, it does not surprise me to hear that the steering wheel heater is also weak. By the way, the steering wheel heaters in our M-B and BMW keep the wheel quite warm on those winter mornings. My 911 is not a daily driver so it is not critical for me.

 

IMO, it's just more stuff that will eventually break. There are advantages to keeping things simple.