. . . as well as her butt ( in the blob ) being higher than the horizontal branch/log in the background?
In the final frame used by Davis & Knights the butt is completely hidden by the sand berm.
I assume you (SG) mean the “log” that sits below the branch to the left of the white tree you initially mentioned, in the first half of your comment. (I’ll reply to that tomorrow.) A “find” (maybe)! (I remember from BFF days you used to come up with these, or something else new, every five posts, so I was bracing myself for it.)
I was just keying on what they claimed was the butt.. It is clear in my frame, that as she walks to the right, the butt is going behind the berm...
But let’s look at some frames in which the butt is nevertheless still visible after your standing frame, and in which no butt-disappearance occurs. In the one below, Patty is directly in front of the white tree and her butt is above the log. There is no trickery here in her butt rising relatively, right? There’s no butt-disappearance, right? This is what her normal progress, before any bending, has caused to shift.
The edge of the embankment is just below her butt. (I consider that it’s the embankment, not the berm, judging by the pair of B&W photos posted a few times upthread, in which the embankment has a rippled edge similar to the one in this image, and in which no high berm (i.e., more than a foot) is apparent (to me)):
Now here are two blurrier images, in which the head has moved (I guess) by only about 18 inches and 30 inches, respectively, to the right. (Patty is beginning to bend.) The first is at most (I guess) six frames (3/8 second) after the preceding one (above) and four frames before the succeeding one (1/4 second). (Patty regularly uses 11 frames to take one step.)
The edge of the embankment is still below the butt, as is the horizontal log on the left (just visible in the corner), right? That stands to reason, because it wouldn’t have been possible, I estimate, for the body to have dropped the 1.5 feet needed to hide the butt and thigh-tops in 3/8 second—the ground doesn’t drop off that sharply. If it did, the top of the head (the white spot on the left side of the head, not the black background above it) would be noticeably lower relative to the branch (or leaning log) on the left
and than the bulging yellowish band around the tree (N and later NW of the head) than it is in the first image above.
A couple of frames later, my blurrier-still, annotated “bending” image appears. (BTW, what I marked as the "left arm" actually isn't—it's background blur, because it rises straight up and ends far from Patty's body. The left arm is invisible, except for the elbow.)
Its butt location is consistent with the ones in the two images just above (higher than the log), and their butt location is consistent with the butt location in the preceding image, and
its butt location is consistent with the one in your standing image. Additionally, so are the locations of the other salient body parts. This continuity is hard to argue against, IMO.