My working hypothesis is that math and crypto are very similar, this kind of error occurs frequently, and you just don't notice. What little crypto I know could be called complexity theory. I've read very little and heard it mainly orally. I've experienced this kind of error, certainly in oral complexity theory and I think in oral crypto. Of course, there's a difference when people are trying to reconstruct proofs that are stamped by authority.

I thought it possible you were talking about the person LF.