"Commonly referred to as The Glorblar Problem"
That phrasing is a cue that the student is expected to either look something up or to refer back to notes or memory of lectures or discussion of the Glorblar Problem in class. Why else mention it, if it were an honest homework problem?
We know they didn't hear about the Glorblar Problem in class - it doesn't exist. For the same reason, we know that hitting the books, either back at the dorms or in the library, wouldn't have turned up anything.
Remember that this is homework, not a test. Yes, presumably the problem is doable without any reference material. The students don't necessarily know that, though. They do know that they've been prodded in that question to at least check their thinking or work against external information....which isn't available to them through the channels they've been permitted to use.
So, the professor deliberately tempted people to look up something online, then amused himself by busting the people who did. Cute method, but it proves nothing other than "schmuck bait works".