benchmarking and retain
Will --gpu-temp-retain ever work with -b (benchmarking)?
The kernel runtime (miliseconds) is too short to produce any heat on the GPU
If only that were true.  I have a GTX 1080 FE that got at least to 73 C when benchmarking.

I was testing it with "nvidia-smi" as it ran.

I will test it again to see if it goes above 73 C.
73°C is nothing to worry about. Up to 90°C should be ok.