I do believe the "B" market is better than it has been but it does have a ways to go viewed as "equal" in many eyes.
I have "B" mares and love them, those mares would be one of the last ones to go if I had to sell. Yet would I bred a "B" stud to my AMHA/AMHR mares, nope. A good horse is a good and I price accordingly, I do also have to price them accordingly if they are going to be "B"'s or not. Meaning I still get better money on my good "B"'s than an average colt but the same colt is still worth more if he will mature "A".
The whole AMHA vs AMHR thing is not as distinct as before. The very, very top AMHA only horses still get traded around for a bit more money than the AMHR only horses but vast majority I see bring the same price no matter the papers.
Personally a growing B market can do nothing but help the miniature market.