While I understand what you're saying, I'm not sure that the purpose of a university education is to "make it fun" for professors.
More likely, the purpose of a university education is to learn.
And that does not necessarily require the professor to happen.
There should never be anything wrong with doing work outside of class, or any implication that doing the work is "not enough". Often learning happens in that time outside of class spent "just doing the work", not "in class" where a professor is struggling to "have fun".
Did you really read my post and see its central theme as being about "fun"? No, of course it's about learning; but if you go into it determined to make it un-fun, and succeed in doing so, you can't turn around and complain about how dreary and pointless it is.
You're also right that learning doesn't necessarily require a professor. But, if you're the sort of student that could learn something without the prof, and yet you have the prof right there, I bet that if you thought about it you could think of some relevant questions to ask that would let you learn more (or faster); and I can almost guarantee that if you're that kind of student the prof would be more than delighted to answer.
As I noted above, the problem is not that doing the work isn't enough; it's that if you go in thinking, hey, I just gotta check every box and I'll get an A, you're a lot less likely to actually succeed in getting the boxes checked in the first place.
I think the key is curiousity. Without it, if the process is reduced to just checking boxes, you're right. Something is lost.
Asking questions is crucial. If you cannot formulate the right questions, you cannot progress in learning.
This student sounds like a self-starter. I just think it's uncalled for to question what he did. Even if he thinks of it as "just checking boxes". He might not think of it that way in years to come.
He did the work. He kept his GPA up.
Hopefully he was intellectually curious and he formulated questions (even if he never got the chance to ask them). If he has aspirations for grad school, "it's not over yet".
There's still plenty of time to reconsider viewing his education as "checking off boxes" and to become more curious.
Meanwhile he did the work. And that's more than many students do.
More likely, the purpose of a university education is to learn.
And that does not necessarily require the professor to happen.
There should never be anything wrong with doing work outside of class, or any implication that doing the work is "not enough". Often learning happens in that time outside of class spent "just doing the work", not "in class" where a professor is struggling to "have fun".