Yes, but even HFT traders use Java and don't look at the compiler output.

Looking at the compiler output is a totally valid concept, but it's definitely a niche case.

If you're doing high performance Java you're definitely looking at the compiler output. At least you should be.

It's arguably more important with Java than with the compiler output for something like C++, as C2 is much more unpredictable and dependent on runtime circumstances. You also want to be real certain that bounds and null checks are omitted as those come at a pretty big performance premium.