I've never seen any suggestion in scientific literature that "nofap" is beneficial or healthy in any way that could be considered self-improvement, though I'm open to the idea.

Too much of anything is unhealthy. From what I've seen of that community it's basically guys who are addicted to porn and masturbation, they do it compulsively, potentially for multiple hours every day, instead of doing other things. If they change that habit they'll almost certainly benefit.