Is it possible that "make up" meant "put together" or "do", instead of "fake up"?
That said, it is a little odd that it made it through 3 reviewers, none of whom objected or got clarification — or if they did, it's not on the record. (edit: which/whom)
I also wondered if there was something less nefarious in the explanation. Was it "Falsify some results" or "Toss up some BS about this topic". The latter is bad, but part of the academic paper business. The first is career ending.
Basic elemental analysis is very easy to fake, and very hard to demonstrate it was faked.
I'm curious what his statement is going to say.
Additionally: it matters just as much how the grad student interpreted the statement, as how it was intended.
Even if meant with good intention, which I doubt, the use of language is in itself poor because the intent is not clear.