There is a fine line between AOWs and Short Barreled Rifles/Shotguns. It’s also fairly arbitrary and inconsistently enforced by ATF. And, despite being told by courts in some jurisdictions that ATF’s AOW rules for vertical grips are no good, ATF will prosecute you anyway. Ian looks at constructive possession:
This has been allowed to stand so far because no-one was sure if the Second Amendment guaranteed an individual right to a handgun or not, until the Heller decision. Now, of course, we have the guaranteed right to possess a functional firearm (specifically a handgun) in the home for the purposes of self-defense.
Given that, I can’t see the restrictions on SBS, SBR, or AOW standing.