I think that rumor got started after too many drunk kids dimly recalled stumbling over it and drew an incorrect correlation between the plaque and their academic woes.
“You know that kid Tyler who practically lived at Psi U? Well he says he walked over that plaque one time and he wound up with like a 1.4 GPA so you gotta wonder…”
I hadn’t. I do wonder how that one got started at what was, until pretty recently, an all-male institution.
I did hear that the only way to remove the curse of the plaque was to have sex on top of it. Notably, the rumor did not stipulate whether an actual partner was required in the, er, curse-removing process.