Remember "everything is a test" in "The Recruit(2003)"?
I suppose the same logic could apply in all interviews, not just ones that might land you a place in the ancient and prestigious institutions like Oxbridge.
If you've done your homework, you'd realise everything is designed to gauge your reaction. Those who are granted such an interview should've expected nothing short of "weird"! They should be grateful to be there in the first place.
People like me(with an IQ lower than Forrest Gump) would never have a chance even to set a foot in the bloody door.