That's the regular grenade. Nothing special is going on except I think they have just received the launchers and are learning together. Thus the presence of the company CO.
He's doing the drills for two men handling.
It was very often used. Although in the book, those are extremely heavy by comparison and the recoil would be extremely punishing...
They may be gathered up close but you have to understand these guys have been through lots and this doesn't phase them. Just grenade handling...