What it makes clearer for me is that our wrists might be very different!
I lift for the back cast with my wrist at maximum ulnar deviation and flip to max radial deviation at the end. The sum of the two angles is less than just from neutral to max extension... on my wrist anyway. But, I think your downloaded diagram indicates a similar thing.
Are you sure you are not also using a different grip in those two photos?
In the photo example of your max radial deviation, your little finger encircles the grip. The other photo is not clear, but it looks like your little finger is laying more along than around.
When I teach I often explain the difference by calling the first one a "suitcase" grip. It is commonly what most use as a default. I try to get them to use more of a "screwdriver" grip. (I think Borger calls it a "key" grip?)
The difference can be demonstrated by asking someone to hold their hand out flat and palm up. Then touch the little finger to the thumb. Two muscle masses become apparent: one at the base of the thumb (thenar eminence?) and one below the little finger (hypothenar eminence?). There is a definite crease between the two.
With a suitcase grip, the last three fingers wrap around the back of the cork handle and trap it against the hypothenar region. It also puts the rear part of the rod at an extreme angle to the forearm. It is common with beginners who think they need to grip the rod much harder than necessary.
With the screwdriver grip, the rear cork handle is placed between the two masses in the crease. The last three fingers do not so much encircle the cork. Instead, the fingers pinch the cork against the thenar mass. This is grip is less natural, but secure enough when learned and, importantly to me, aligns the rod much closer to the forearm. The rod becomes almost a straight extension of the upper arm, the wrist arc smaller, and allows fewer degrees of freedom to screw up tracking.
But, as I have said before... I do not believe one size fits all.
