Meggers from 15xx onwards will in all cases handle phase to phase on high-current. The 15xx gets very upset if you accidentally select no-trip and connect phase to phase. The manual says it isn't 'supported' but doesn't talk about the undocumented internal fuse! The 17xx onwards just beeps.
It can be the case (not wishing to cast general aspersions) that college tutors have been out of the day-to-day game for a while and not been exposed to more recent equipment. He is right that you could once easily break a tester doing this:
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By the time Robin became Kewtech (in simple terms), the KT63 doesn't blow up but also doesn't handle phase to phase.
So in general, if you have a Megger, crack on!