> The heuristic can be reworded as adult parents are more knowledgeable and capable than children.

I think that's true in general, but when it comes to making decisions about the child I think that has to be weighted against another heuristic that's often but not always true: that people know what's best for themselves better than other people do. I think people often wrongly neglect that principle when it comes to children assuming that they don't know what they're talking about without taking the time to listen and understand their point.