But for the situation existing: is the BW specialised for the states for examples used by any expertising company so that the catalog numbers appears instead of SG? From what I heard and saw, SG is still the way to go for the expertizers.
I couldn't answer that question, I have not had experience with expertising.
Personally however, I would most certainly prefer an Australian expertiser look at my material for appraisal, then whatever reference he/she would attribute, would be acceptable SG or BW.
I don't feel any catalogue can be "too specialised"
I would feel if a variety received a BW attribution in a certificate, then that would attract a high Marque for the owner.
I would consider BW to be the "Bible" of Australian philately, yet it is still not perfect, nothing can be in an evolving study.
Just my opinion of course.