It doesn't matter if you can or cannot replace it with other words. It's what the industry has decided is an appropriate term to use in the circumstances.

> in addition to being vague and essentially meaningless in most contexts

It's not vague, it has a literal meaning. Efficient. The definition comes from the French word "performant", the meaning of which goes back to the 17th century.

This isn't people going "ohh it's related to performance, let's make up a word that sounds similar", like "supposably" or similar.

It's "Let's take an established word with the same roots that has the same meaning as we want and use it".