It's the handstand, and that's about it. One page out of three novels, and they're derided as the worst books ever.
That isn't to say they're good, because they're not - but they're mediocre rather than offensively bad, there are far worse novels in the Dark Age line. I think a big part of their bad rep is that relatively few hardcore fans have read the Dark Age books, and the early ones got a disproportionate amount of attention and therefore more ire than later ones.
(for the record, I'd put The Ruins of Power and Phadera WeldonIlsa Bick's Dragon's Fury books as worse than the Proving Grounds trilogy without a moment's thought)