Claiming that because they made the most popular routing library for React it's shady to provide tutoring about it for profit is very much of a stretch in my book. Care to explain where exactly is the conflict of interest? Does that mean it's also shady to work as consultants? Where is the line drawn?
Do you really believe that noone is going to call them out if they started doing things deliberately to maximize profit (i.e. breaking changes without actual improvement, harder to understand than necessary APIs, etc)?