I think each presents in their own style - as a reflection of the times in which they live and work.
Jeremy can be abrasive if someone is esepcially dense, but given that by definition, these people are all potential or substantive graduates, and represent the intellectual cream of their university (or at least the ones who wanted to be on TV anyway!) an assumed level of knowledge can be taken for granted.
I think you will find that his off-screen banter and interaction to relax everyone will ensure that all who receive a Paxo'ing will know he doesn;t mean it.