That was typical before some students got handed a lot of dotcom boom money.
(And then somehow most interviews throughout the industry became based on what a CS student with no experience thought professional software development was about. Then it became about everyone playing to the bad metrics and rituals that had been institutionalized.)
You can ask questions based on a resume without them disclosing IP, nor the appearance of it.
That resume-based questions thwarted a cheater in this case was a bonus.