Yeah he's probably just one of those people who has built up an on-screen persona of being tough, patronising, arrogant, condescending, not suffering fools gladly... away from the camera he's far more relaxed.
I don't think the questions are necessarily easier or harder between the two ears of UC. It varies anyway year on year, let alone between eras. For every stinker from Gascoigne's day you can find an easy one. There's a snippet on youtube where it's essentially "for 40 points, name five scientists important in overturning the old view of the Solar system" -- and, after rattling off Kepler, Copernicus, Galileo, Newton and (say) Tycho Brahe, the score racks up so fast. Or you have "Solomon Grundy was born on Monday. When did he die?" But then from Paxman's era you have questions such as "what is the 8th prime number?", that's really just testing speed of recall rather than knowledge -- and there was perhaps a heavier emphasis on literature in earlier days that might have more students stumped nowadays than before.
Good luck to your son, Hopkirk!