I don't know if he actually said this, but power limits on gpus do work. I've been limiting my gpu to about 60% max power during long AI workloads and I lost about 10% of performance. A 40% reduction in power usage seems worthwhile.
same here with the 3090 I use. Power limited to 60% and I barely notice a difference when experimenting around with AI or playing games. Really good to use in a SFF PC
It probably depends on your gpu though.
Undervolting would probably be even better.