I think part of the confusion here comes from the term P-51 Mustang, which is often used to refer to the entire NA-73/Mustang family of model, also designates a specific variant within the family.

Given that the NA-73 was designed as a fighter and that the A-36 was derived from it, it does make sense to state it is the dive-bomber variant of the P-51 Mustang rather than the opposite. The alternative would require going into details concerning the designations and lineage of the entire Mustang variant family, which is quite beyond the scope of this short, one-paragraph article.