Are powerful ingredients classified as “middle/Heart notes” with long tenacity comparable to base notes?

I think of top-middle-base as describing broad roles in a fragrance rather than a direct mapping from a material’s quantifiable attributes. It’s both relative and multifaceted. Longer-substantivity materials are more likely to perform base note roles, but odor strength, projection, odor character, and the composition of each blend all factor in

With something like pharaone I think of it as powerful (intensity) and projecting enough that it will tend to be present and “taking up space” throughout the heart. But in a blend with an otherwise powerful heart, very trace pharaone, and few other materials dominating the base, it would perhaps function mostly as a base note.

On the other hand, a more firmly “base” material like benzoin will lend some character to and modify the heart, but in most perfumes is not likely to comprise the main theme of the heart, as more intense materials like florals will tend to be taking up space there. This of course wouldn’t be the case in a perfume designed to feature benzoin (but to do so you would need some heart-y materials to support the theme if you want anyone other than you and your dentist to be able to smell your perfume)

These categories are useful in that they present the largest possible buckets in which to classify materials and organize our thinking, but ultimately every material will play a slightly different role in every blend.