My best guess is that Gemini was trained on the textbooks that the questions are meant to test against, thus they are probably better at explicit recall of those questions or related questions.

This is a pretty limited introductory course based on what it says in the methods of the paper itself.

That and the research is done by Stanford’s HAI institute with an obvious bias and the paper is curiously missing a conflict of interest statement.

EDIT: just found out that Google is a major donor to HAI. So this research is at least partially funded by Google. Which is probably the reason the authors fail to declare no conflict of interest.