I can just about believe that this kind of scenario might be a very rare exception where the performance difference is relevant and you might want to do something else.

Still, color me skeptical.

"In simple enough scenes"? OK perhaps, but we don't want to only run ray tracing for very simple scenes. Simple scenes are those cases where you probably don't need much calculation, so does it really matter that 5-10% of that simple calculation is RNG? It's the complicated computation-heavy scenes that matter!

Also, one would have to see the code to judge this. For instance, maybe that code was wasting random bits a lot?