This series continues to impress. As a grad student, I have had more or less this same conversation with multiple undergraduates that were also interested in pursuing a graduate degree. It's one thing to find a field interesting (mine was physics), but it is a whole other thing to become super-super specialized in one tiny part of that field for 5+ years while making next to no money. Some of those students I spoke with did ultimately end up pursuing their Ph.D., but several others have gone on to do other things. Some notable ones are one became a marine biologist, another founded a non-profit, and one a medical doctor.
This conversation is exactly what Shinji needs to hear before diving into graduate school. Huge credit to the professor here, and for the author to depict this kind of conversation and force the introspection that Shinji needs.