And some of the optimizations that do exist are interesting. I wonder if, post-Spectre/Meltdown, the old side channel results involving Python's integer behavior would be more widely viewed as problematic.
These are distinct from eg Spectre because the point isn't isolation breaking, it's leakage. But at least a few years ago there was always a question of "are side channel attacks real", and I think we're pretty clearly over that question now.