Why do people say that Khan and Haye have gl chins?

Wlad does have a gl chin, as does Khan. Both were evidenced in the ring. David Haye is more of a sticky wicket in that yes, he was knocked out by a light heavyweight, but Haye was also seriously ged out. Haye used up all his anaerobic energy while chasing a KO. That's more of a loss due to a tactical error rather than gl jaw. I don't think Haye is all that rugged, but we haven't seen any evidence of "easy to knock out-edness" at heavyweight.