I followed the Macrumors thread for a good while and there was speculation that it might even have been a hardware flaw; something about needing to run the memory clock at full speed to prevent flickering when driving different resolution screens.

Apparently there are some AMD desktop GPUs that exhibit similar behaviour, but obviously an extra 15-20W draw is far less of an issue in a desktop than a thin laptop.

Either way, this machine is coming up on two years old. It’s not gonna be fixed, ever. I already sold mine because of it.