Stop bending your knees and sticking your butt out in the setup, note how your spine is extended and body tense.
Stand up and relax, only slight bend in knees and hips, spine into flexion navel tucking toward belt buckle so your shoulders and arms hang loose and can swing freely.
After watching that video I am confused because it seems to be saying that your pelvis should be tipped forward at setup and progressively lessen tilted forward as you swing. I think that is what I am doing? If I look at where I am just before release, I think I've reduced pelvis tilt quite a bit (although not enough so that I get to a slight flexion of the back as was being discussed in the video).
In any case, I'm setup that way to encourage me to keep my balance point more over my toes. When I don't set up that way, I tend to end up staying vertical through my swing. That and I didn't want to start out hunched over, like I've been sitting improperly at a desk my whole life or something.
But I'll work on being more relaxed at the start.