Premature optimization is more about not home-growing some bespoke fancy data structure before you've even ran the application for example. If it's a bottleneck

Premature optimization is more about not home-growing some bespoke fancy data structure before you've even ran the application for example. If it's a bottleneck you can optimize those pieces later. Requirements can also change. Now you've spent a ton of time building something fancy and are less likely to throw it out because you're attached to the big fancy work you put in because we are human.