I have it on good authority that Ayoob "monopodded" (grounded the mag and used it as a balance/pivot) his AR at the Appleseed he attended, and did not use the sling properly, and was resistant to learning the technique as presented by the instructor. He got "called" on it twice and instructed to learn the proper prone sling techniques that function with any rifle (even ones that don't have big box mags sticking out the bottom), but refused to do so.
He's not nearly the genius he is credited with being.
(Yes, monopodding is a legitimate technique, but it's not the course material that Appleseed presents. Try monopodding a K98 mauser, if that's how you stabilize for a shot. Monopodding is platform-specific, Appleseed is "any rack grade rifle plus surplus ammo plus competent Rifleman equals 500 yard hits.")