I agree with the “premature optimization”. It’s one of those phrases like “correlation does not imply causation” that makes my blood boil. Like cool dude, did you just take freshman CS.
You'd be amazed at how much experienced programmers fret about local "optimisations" that are actually made irrelevant by the compiler and just serve to make the code harder to understand. And with incomprehensible code comes actual errors, not just slowness.