I agree that true opera study should wait until a student is older. I was referring to actual legit styles and classical technique from an early age and only because it's important for any style. For instance, vowels are more important in classical technique than musical theater; therefore, if a singer desires to continue classical style, rather than mt, they will have trouble with the vowels.
Again, like you say, it's just a difference of opinion, and any student needs to work with the teacher they feel is suiting their needs. The original poster should seek out the teacher/coach they feel will give them want they want.