Not meaning to couch-quarterback things here, but most of what you're seeing in Dave LaRue's video is the result of a poorly balanced instrument. I don't think DL is at fault, he's clearly just coping with a poorly fitting and imbalanced bass as best he can. The telltale symptom is the headstock-in-the-next-county syndrome that's common on basses like that one with teensy upper horns and a lot of neck-heaviness. You can see how far his arm is stretched out when he goes back to half-position to play the low F and just move around in general in that part of the neck.
So, to bring this back to the original topic, this is a good illustration of how untreated poor balance can completely impede a comfortable technique. He tries to maintain the same position as he goes down towards the neck, but he just can't do it because the instrument just doesn't let him do it with good physical economy.
Contrast that with the Gary Willis video, where the instrument has better balance. He doesn't have to reach out into the next county to play in the lower areas of the neck, so hes able to stay in position down there a lot better.
Another cause of the headstock-in-the-next-county problem is insisting on placing the instrument between the legs classical-guitar style when playing seated. This looks classy, but with a long scale bass, it can cause the same problem with being able to reach the lower part of the neck in an ergonomic way. Placing it on the right leg instead (RH player) moves everything over making that part of the neck easier to reach. The compromise is now the upper registers are harder to reach, but then you're much more comfortable down in half position.
As for the braces/splints, I don't think that's what those are. I may be wrong, but I think they're just the little towel things that keep the sweat from running down your arm onto the bass....
L