Since AA developed the chamber, cartridge, and bolt, took part in what was submitted to SAAMI, etc, it seems only natural that AA's version would be considered the industry standard. I think any bolt or barrel manufacturer that deviates from that standard will be limiting their own opportunities. And even a barrel maker that offers variations based on bolt design will likely cause more headaches and confusion. We've already seen it with BHW barrels and "Type 1" or "Type 2" bolts. Similar stuff with CSS barrels and "CSS" or "OEM" bolts.
Drifter