To extent his reach (arm connects inside upperarm) and rotate his body- to what we call his third point - and take his balance. When I watch a bit further I see fragment of how we start shihonage. Also he tends to move around the center of movement. We make ourselves the center of movement. Aite is more or less a satellite in our approach. Would this be exemplary of IS applied in technique?
The arm drag is not exemplary of applied IS, I guess most of the time anyway. But a good arm drag may as well be... iriminage? One side allows them to go their merry way, the other goes your way, in that case launched from... a parallel stance. If they resist the pull, well, more solidity for you to pull/drive yourself forward. If they don't resist, well, they just get... dragged. Fun side-effect of good external movement, one side drives the other, the other side drives the one. Did you push off them, or they push off you? Oh, looky that, you now have their back, what fun you two shall now have! Callooh! Callay! If you are invested in the outcome of who is the satellite, and who moved in absolute positioning in space, rather than in the relative positioning of the bodies, that belies a certain fixation on outcomes that is not becoming of slaying Jabberwocks.