Love me some 2hbh pics from behind .... you can learn a lot ... good job grabbing the pics.
Let's just start with one of the most important things you got right (

... I kid, just having fun ... what you got wrong at the bottom)
You made the distinction of left arm taking over at pic #5 and not pic #6 (the slot). Exactly right with these type of 2hbh swings ... left hand becomes dominant (still don't like your terminology left arm takes over ... like becomes dominant better ... discuss later). Left arm is still pretty relaxed at the slot ... and stays relaxed for a beat or two until around pic #5 and then in fires into contact with good extension. Not all 2hbhs are equal ... Venus ... IMO ... goes left hand dominant from the back of the backswing.
LOL ... I was typing the post above about the 2hbh version of your "strokes are segmented" ... and suggesting you post 2hbh discussion and pics and video in that thread. And then you included it in this post.
OK ... rather than going point by point in your other remarks, I will just tell you things as I see them, some are different than what you see:
- first thing to note is look at left foot in pic #2 ... off the ground ... no load bearing on left leg ... left hip was involved in the unit turn, but has NOTHING to do with the uncoiling. It's a step to the front foot carrying the unit turn to the front foot ... left hip DONE.
- so when we say "hips" on this stroke in the forward swing, we are talking about the right/dom hip. The line on his shorts on his left side is only relevant as far as indicating in rotation around his right hip.
- next question is when does Djoker start to rotate around the right hip ... I would say at the slot (pic #4). This is important so some more words here:
The exact moment rotation around right hip ... pic #3 or pic #4 isn't the key ... no doubt there are some small timing variations among pro 2hbhs. I would say the following is key on this point:
1) drop of arms/racquet to slot, and setting lag are all synchronized with the step and getting up on front leg. It's not ... drop and then step, and it's not step and then drop ... it's drop and set lag while stepping and getting on to front leg. I have looked at quite a few pro 2hbh video, and this is pretty universal across pro closed 2hbhs. I think it is major in smooth rhythm and power.
2) So until the slot (pic #4) ... either no, or no substantial hip or shoulder turn ... just very relaxed arms going down to slot setting lag. Note: there is no stored energy in the lag ... it just gets set with VERY relaxed arms, with no powering from shoulder rotation. Any stored energy/stretching (which I really don't buy much ... and certainly beyond rec 2hbhs imo) would be shoulders turned past hips in unit turn, and passed forward to right leg with the step. Then when the uncoiling/swing starts ... maybe you have some shoulder stretch beyond hips to release.
3) put this as a numbered item by itself ... there is no "hip turn first" followed by "shoulder turn". When rotation starts around that right hip, it's a full torso rotation including shoulders. If you have turned hips to their max, and then shoulders to their max past hips in your unit turn, then by definition there is no such thing as starting with just hip uncoiling ... the shoulders have to come with the hips.
So here is what happens ... it's not the right hand pulling ... or any Macci fh yank at the slot.
1) first part of the swing over the right hip rotation can be thought of as "shoulders plus upper arm" rotation. You have all the lower k-chain stuff making that happen ... but the delivery at Djokovic's initial swing forward in his shoulders and upper arms (the two arm unit being swung together .... as you said, left arm hasn't taken over yet). I put it this way, because Djokovic and power the hockey out of his torso (hips, core, shoulders) and still have very relaxed arms and hands clear up to pic #5 where the left arm needs to make some pretty active effort (if you want to call that not relaxed?). Djokovic's relaxed arms and hands just navigate to drop and set lag to his desired position at the slot ... you can look for a Macci butt cap yank until the cows come home .... Macci is selling bs on that one with the 2hbh. I will post a video at the end to make my case on that one ... since I hear in my head "Macci has taught pros and you are a rec player ... yada yada yada". Don't care ... like some of Macci's stuff ... don't like this one.
*** Sometimes with the pros the full lag is set at the slot, and other times, it's partially set and then goes to full lag immediately after forward swing starts. This is how I view it (and actually set the lag myself). NYTA said he did it the same way. To me ... it's like a waggle at the end of my loop at the slot. I just let the momentum of the racquet coming around at the slot with relaxed hands carry the rh around (and down if doing that on that shot). I don't hit a static stop point ... just continued momentum from waggling at slot immediately swinging forward. It would take video review to see if full lag has happened right before the hands go forward, or it completes to full lag (like many pros) immediately after hands start forward. In either case ... it is something completely different than the fh butt cap forward move that then sets the lag.
2) completing the swing ... Djokovic's left arm becomes dominant around pic #5 above.
OK ... if you are Macci want to stick with the 2hbh yank butt cap forward lag myth ... both of you should do this and video it and post it here:
Love this guy's video. Go to 09:00 in the video, and watch the drill he does for FH. Go do the same drill with the 2hbh ... video it and post it.