This is one of my favorite mechanics topics in DG since I've had so much trouble with it myself, and I don't think it's a coincidence that the
Drive Leg thread is so long and there is a big confusion about "back leg" or "front leg" throwing etc. I lurk a lot of form threads here, and it's fascinating that you get a lot of pretty young, pretty athletic people with good levers that get trapped in the 450-500' range. One of the things that they usually have in common is that their body isn't moving in a way that lets them get that minimum-effort, maximal leverage move off the drive leg. They have issues with (e.g.) horse stance or posture or are not "riding the bull." They aren't doing what Jan Zelezny learned to do with the javelin:
I do think it's mechanically fair to say that the action is the same (or close enough) to a standstill that it makes sense to learn it well there. I never regret the time I spend working on standstills and usually find that the x-step gets better afterward - the same is not usually the case working in the other direction. I do also think that (re)learning the x-step is hard because you need to figure out what works best for your body in transition and with more momentum after that.
Focusing on the rear foot "rolling in" in swings or Hershyzer drill and how it naturally works in Swivel stairs all helped me. Like pretty much every drill, I even was doing Swivel stairs wrong at first due to my posture so that can be worth posting too.
You were also still extending and tipping off the rear leg in the most recent vids rather than shifting and dropping. What Paige is doing here is exactly what I learned in standstills and focus on finding in the x-step:
These imgs helped me understand it better thru x-step. Try to see through the details and how it's basically the same thing as the golf wireframe up there.
https://www.dgcoursereview.com/forums/showpost.php?p=3859653&postcount=70
*Edit: Also, I'd avoid AB. He throws with a lot of s-curve in his spine and knee snap as SW pointed out elsewhere (both are bad news for the body in the long run in other sports). Barela has nevertheless loaded better into the rear side like riding the bull or Double Dragon without being horsestanced and has a better tilted axis than you, which is why your upper bodies look so different. His front hip is clearing and leading the swing. Yours is kinda bracing you harshly against the forward momentum of your body because you tipped into the plant rather than shifted w/ a tilted axis.