I think a hard rule like that on the mechanical side would be super helpful. Having a clear minimum standard for playing the race correctly, and then additional roleplay recommendations would make me a lot more comfortable deciding where to draw the line. (My personal line will be a good deal more strict than the baseline suggested, but with the potential of both social and mechanical consequences for not playing that Celestial aversion correctly, a clearer guideline would make me feel a lot better about potential balance issues like access to magic carriers.)