moving the goalposts

You met the standard. They raised it.

Wrong: “Show me one benchmark.” “Here.” “Well, one benchmark proves nothing.”

Right: “What would actually change your mind? Say it now.”

The original request was satisfied, so a new one appeared.

The tell is that the new requirement arrives after the old one was met, and would have been easy to state at the start. That timing is the whole fallacy.

How to answer it: get the standard specified in advance, in writing if it matters. Then when it moves, the movement is visible to everyone.

Now go write the standard down first.