> you could say preconceived just as easily
Would have saved us from all the people who reject any sort of optimization work because for them it is always "too early" since some product team wanted their new feature in production yesterday, and users waiting 5 seconds for a page load isn't considered bad enough just yet.
Premature optimization doesn't mean "We have an obvious fix sitting in front of us that will definitely improve things."
It means "We think we have something that could help performance based on a dubiously applicable idea, but we have no real workload to measure it on. But we're going to do it anyway."
So it doesn't save us from anything, it potentially delays launching and gives us the same result that product team would have given us, but more expensive.