This seems to be almost universally true.

If it's true, I would say because there should be less barrel whip. Just a guess.

My Rock River 308 is very accurate

Good to hear that - I was referring to 7.62x39 Soviet though.

May be partially due to the ammo available.
Most people don't hand load for an AK, and there are a lot of ammo factories cranking out cheap ammo for 7.62x39.

Also, less recoil on the 5.45 makes it easier for a lot of people to shoot than 7.62x39.

Just my take on it..................

Makes sense. There is a video on Youtube of AK's & AR15's firing side by side in ultra slo-motion, and there is noticable flexing of an AK action when it fires.

But part of the appeal of the AK is better terminal ballistics (or at least bigger holes via .311 bullets) so I have little interest in a 5.45 AK