As a hiring manager, I find talking in detail about work (school or industry) a candidate has done is a lot more illuminating than a coding problem. The trick is that it takes more preparation and focus from the interviewer because they need to know how to ask the right questions, they must know how to guide the conversation in real time, they must understand details about entire project in a few minutes, etc.
How do you know they personally solved a problem, rather than just studying someone else’s solution?
I find going into the technical details of projects on the candidates CV quickly sorts them out.