I did once have a Physics lecturer say " When I took Quantum Mechanics back in my undergrad, I got an A but didn't actually understand anything" and then in the same lecture 20 minutes later: "What part of this do you not understand?" when the entire class was just blankly looking at the whiteboard.
At least at the undergrad level, it's not impossible to get an "A" without actually learning anything. Especially Freshman/Sophomore level classes. You just cram for the exams and regurgitate what you memorized. Within a few months time it's mostly gone.
