Kelly's Irish streak would likely see him take them to the barriers. Meaning he was seriously tough in a time where most good riders of his skills had to rely mostly on their own efforts. I disagree that they weren't at the top end of GT's; just that they attempted to do everything else in the same season unlike most true GT riders.
In the book, Sean Kelly: A Man For All Seasons, Kelly makes the point that building your entire season around a Grand Tour, was a risk he was never willing to undertake. Greg Lemond once said, "On his best day, there was nothing you could do against Kelly. He climbed better than the best climbers and sprinted better than the best sprinters."
Commentating on Eurosport, Kelly once said Valverde's Palmares was very impressive and finished by saying chapeau!