It's the legacy thing. The invincible aura that has surrounded both of them for years. Bones is a top fighter no doubt and has an incredible resume, but he just hasn't been that guy for that long yet.
I think it's quite the opposite, GSP has seemed more human with every year (blowing out his knee, nearly get finished by Condit) while Jones hasn't been challenged once yet in a few years of fighting in the UFC. If anyone seems invincible it's bones, silva, aldo and jds