When I look at your picture in the opening post, all I can think of is "nope". Getting most of the way off the bike while it's moving just doesn't make sense to me. Sort of like jumping out of a perfectly functioning airplane while it's flying along. Maybe I'm just old. I do spend time practicing figure 8s and circles and u-turns and quick stops in a parking lot, just to build the muscle memory and skills, but aside from shifting my weight and experimenting with different lean angles, my rear stays planted in the seat.
Which brings to mind something I've thought about when practicing. I found that I have a tendency to keep my torso upright when leaning the bike into turns, which means Bike has to do more of the leaning. It takes some thinking to shift my torso over to counter balance so Bike stays more upright and has more lean angle in reserve.
Does anyone else struggle with that? I'm thinking it might be because I spent a lot of time on horseback when I was young, and it was just natural to pivot at the hips and stay upright when the horse was moving around.
Well, you say it doesn't make sense to you to get your body off the bike but then later down in your post you say that if you keep "your torso upright when leaning the bike into turns- the Bike has to do more leaning." That's exactly the reason we hang off the bike, so that we can get around a corner faster with LESS lean angle. If you try and stay upright on the bike or don't hang off at all, you use MORE Lean angle and are apt to run out at some point.
Now, such aggressive body position (like my pic) is more relevant for sportbike riding, track riding, racing and is less necessary for for everyday riders, cruisers, touring bikes. But, you will still want to get that upper body "going with the bike."
Instead of making it complicated, you can simply think of trying to allow your body to remain relaxed and follow where the bike goes.
Do you ever take a passenger on your bike? You know how it feels when you try and take a right hand turn and the passenger stays upright or leans to the left? Riders are often like bad passengers on their own motorcycles. Try being a good passenger on your bike and just allowing yourself to lean with the bike.
What are some other benefits (besides using less overall lean angle) of getting body position correct and being a good passenger on your own bike?