Currently just a bunch nonsense, for example, verification checks for metalness map on models that doesn't have metal parts/not made out of metal but don't check for AO wich every PBR model should have, that's optional... It checks for assigned materials even if box "materials" isn't ticked. It check if geometry is non-manifold on low poly models that are created exclusively for games... There is more... but If you try to justify verification, you will just end up with an unoptimized asset when it comes to real time/game models.