Uhm, without looking too closely, all of them, or at least the first couple of FHs, beloning to Nadal and Roger?
Anyhow, like you, I had some doubts for the neutral/closed stances (like I use), I believe the Doc meant it primarely for open stance.
If one object is 'over' another, then a vertical line, as shown by a plumb bob, from one object would go to the lower object.
1) First,
when during the hand's path does it appear over the left foot?
2) Is it when the hand reaches its farthest backward point and turns around to come forward? For the hands at their farthest points back, I see the hand as well back from the left foot, sometimes by 2 feet/0.6 meter.
3) Is "over the left foot" at some unspecified time, only an instant, during the hand path? When?
4) Do we ignore how it would appear from an above camera view?
An image is two dimensional: 1) the dimension up-down in the frame and the dimension side-to-side in the frame are well shown. But the 3rd dimension toward-away from the camera is shrunken or even hidden.
For a camera at ground level, a hand can appear over a foot from one camera angle. But as you move the camera around the player, from other camera angles the hand would not appear over the foot. Only if the hand were truly over the foot, and a plumb bob showed that, would the hand appear over the foot as the camera was moved around the player.
If the main take away of a reader is that
I should have my hand over my left foot, then tennis terms have misled again. You can literally place your hand, at its farthest take back, over your left foot. But what was intended?
What is seen in videos from different camera viewing angles?