As a fellow PhD candidate, I can confirm that this sort of thing happens pretty regularly. Basically his advisor wouldn't take the risk of making the claim so h

As a fellow PhD candidate, I can confirm that this sort of thing happens pretty regularly. Basically his advisor wouldn't take the risk of making the claim so he made his student do it, then put the onus on the student of "clarifying" this claim. If the claim works, they share credit. If it does not work, the blame is solely on the student for making a bad claim. If this is a seminal work, then it puts the student in a terrible situation if they want to pursue this line of work.