Jim,
It shows what I've spoken of and read. The inertia spring action, in the bolt, happens for only part of the recoil cycle. When the spring uncoils, it starts the bolt rearward, but the recoil is also going in that direction too, which is countering to the bolt, however, the recoil speed is slowing down, where it will soon stop. The speed the bolt travels overcomes this, due to the recoil slowing down and the springs kick, so the slowing recoil helps it along, and when the gun slows to a stop, on the shoulder, the gun reverses direction, due to the shoulder, and goes forward again, increasing the speed the bolt has going back, until it goes as far as it can, then cycles with the bolt follower spring, (or stays back, due to no new round to release it). The bolt may reach its full rearward stroke, before the shoulder stops the gun, and the muscles cause it to go forward again. That I do not know, and it's not shown. Either way would work.
The cycle is similar to a cue ball, sitting stationary, which is driven against the rail of a pool table, over the sudden movement of the table shifting under it, where the cue ball would then change direction, after it meets and compresses the rail, which sends it backwards. However, in this case, the table would be moving, (recoiling), in the same direction as the reversed ball, which wouldn't work well, unless the tables motion had the brakes applied to it, (the shooters shoulder), slowing it down. It wouldn't work at all, though, if not for the recoil, (or moving table), to set it all in motion.