It's unfortunate that performance is so rarely considered to be a feature.
Not much on .0 versions, those are more feature packed, but all the other time.
Occasionally, there are cases that could be argued to be exceptions to the general rule. But that's a hard argument to make -- everything committed to a back branch is officially a bug fix. Things like optimizer regression fixes are "performance enhancements" in a certain sense, but are nevertheless justified as bug fixes.