Support, overcoat and addenda probably contribute to this character difference between papers. IDK.
Azo is characterized by being coated on a specially tinted SW baryta with a warm tone pigment added to the support. No other current paper support that I have seen can reproduce this subtle effect.
I would have to do a lot of research to give you more detail, but superficially, they are quite similar.
In fact, early on, each grade of paper was a mixture of the high contrast and low contrast emulsions in different proportions to give the final desired grade. This is often true of a given type of paper.