I work on OSS-Fuzz.
As far as I can tell, the author's PRs do not compromise OSS-Fuzz in any way.
OSS-Fuzz doesn't trust user code for this very reason.
Fuzzing isn't really the best tool for catching bugs the maintainer intentionally inserted though.
After all, if it hadn't had a performance regression (someone could submit a PR fixing whatever slowed it down, heh) it still wouldn't be known.