I think that how come people on reddit talked about foiiling was related to right brainness. Specifically, they mentioned that they would first do many (a few?) of the problems and then after a while their brain (I’m considering this their right brain) simply did the calculation for them and they had trouble doing it in the L-mode (rather than r-mode = right-brain mode). This makes sense because the right brain is non verbal and they did not quite understand how they were getting the answser (because r-mode is unable to verbalize information).