Might be the wrong sub to ask? Maybe better to check with a Russian military sub, if there is one. It does seem a comfortable way to grip an AK-style rifle.

Hey - I've removed it because it's not really a history question. As an ex member of the New Zealand army though I can tell you that is a very common method of carrying a battle rifle across all military countries, including America. It is called "cradle carry" and is done because it allows the firearm to be horizontal for a long period of time. It is the most comfortable way to carry if you are not wearing a webbing belt. The barrel dropping is not considered best practice as it takes longer to bring the rifle to bear - ie to go from threat to fire.