Firstly, thanks (?) for digging up two long-dead threads on air brakes for your first two posts to Stovebolt, ever.
There is no air brake
endoresement, but there is an air brake
restriction if you fail or do not take that test. Somehow, it's assumed that if you have a CDL, you passed the air brake test. The other skills (haz-mat, combinations, etc) are the other way around (use endorsements). I always thought that was weird. But you are correct in that the presence of air brakes does not make a vehicle a CMV.
Still, I think it is or could be all moot: CDL requirements are not applicible to "vehicles operated by persons only for personal use, such as recreational vehicles and rental moving vans." (Virginia Commercial Driver's Manual July 2010). My state law also excludes "any vehicle when used by an individual solely for his own personal purposes, such as personal recreational activities" from CMV/CDL requirements. The
feds also include in their definition of a CMV "used in commerce to transport passengers or property". CDL/CMV requirements are generally uniform thoughout the states (Unlike IFTA).
Does this mean you won't get hassled by the DOT man? Sure, it can happen. That's life.