Treat the reverse K as an illusion, not a big spine tilt
The speaker says that leaving the sternum still and bumping the hips forward only produces a couple of degrees of spine angle. He explains that the reverse K looks bigger than it is because the trail hand reaching lower on the grip drops the right shoulder a little. He frames the reverse K as more of an illusion than an actual large spine tilt.
Channel: PorzakGolf
Watch official source at 2:41