I feel like we’re all over the place here. When I say what if Nani wants to study something other than marine biology, then it’s a “slippery slope” and why not change everything about the movie, when the writers add a new plot line, it’s a “small plot point”.
Look, here’s the summary of my views: I think a preponderance of evidence points to the idea that this was a change the filmmakers added intentionally, to highlight a particular perspective on healthy individualism. I don’t think their hand was in any way forced by plot constraints. For one, they were the ones who added the new storyline, and for another, we have the Forbes piece which the director says highlights his views.