I once heard a cute Vort about that. Reb Akiva Eiger points to the Halacha that one musn’t sit on a Kever. I don’t know who said it, but the way the Vort goes is that this Taana sat on it to show that it can’t be.
Anyhow, according to the Maharal that I mentioned, he wasn’t referring to an actual Ben Sorer Umora.