Perhaps he didn't want the more specific word? Fast means fast, great, I get that. But what if you want fast code that works consistently, "performs" well, if you will. Then performant efficiently fills an appropriate niche.
I am not sure if that is the goal of the original statement, but the point stands nevertheless. All words were just made up at some point of time or another and it should be trivial to prove the set of words available in any language's vocabulary is a very small subset of the set of all ideas one could possibly express; for this reason I think the creation of new words should not be discouraged unless there is a compelling reason to do so.
In the end, the word accomplishes what language ought to: it conveyed an idea which was more or less understood by the target audience it was aimed out.
I am not sure if that is the goal of the original statement, but the point stands nevertheless. All words were just made up at some point of time or another and it should be trivial to prove the set of words available in any language's vocabulary is a very small subset of the set of all ideas one could possibly express; for this reason I think the creation of new words should not be discouraged unless there is a compelling reason to do so.
In the end, the word accomplishes what language ought to: it conveyed an idea which was more or less understood by the target audience it was aimed out.