He's the only one i've seen yet do that particular flavor, so ill just call it the Davis transition. He's forcing half guard to trap the bottom leg then pulling the top leg into the back turk/hiplock position.
Pretty much every single position where you are stacking or controlling the opponents legs in some way is an opportunity to transition into the leg turk; single leg stack, double under, over under, cradles, triangle or arm bar escapes... you name it, you can see the opportunities everywhere. For example, the classic berimbolo from DLR itself works by putting yourself into a back leg turk, only upside down (whereupon you can switch the legs into the leg ride/truck, or just come up on top).
Strong moves attack weak anatomy. People are strong on the front plane, and weak on the back plane; its how humanoids have evolved. Ergo, most strong moves are moves that give you a back angle; you can see it in the arm triangle, the russian 2 on 1, the duck under, the front headlock, the saddle, the leg drag, and more. If you look for it, you will find it.
Alignment brings strength, misalignment brings weakness. When your opponents spine is twisted and tilted, he loses his power, he becomes weak. Ergo, most strong moves are move that compromise your opponents alignment. When he is misaligned, his muscles are no longer in position to coordinate naturally, his kinetic chain becomes broken; he cannot transmit power from one point of his body to another, it gets lost into a mudhole of squish. For you or your opponent to successfully escape, counter, or execute any move at all, he must first bring himself into alignment to be able to exert force. If you look for it, you will find it.
Push pull, up down, forwards backwards; humanoids are optimized to move linearly in cardinal directions, but are weak at the sides. Ergo, most strong moves are moves that put your power against the flanks of his power, collapsing his structure, and putting him under your control. Spiral motion exposes hidden flaws. If you look for it, you will find it.
Flanking, misalignment, back angles; these three principles are key to ground fighting success.