My biggest question about WP is - is it a biomechanically fair thing to be asking horses to do? To my very English eye, they all look like they are moving very uncomfortably - and I don’t buy “they are bred that way” as a defense because we quite happily have bred all kinds of physical deformities into dogs for the look or movement (American German shepherds anyone?) so the fact the animal naturally moves that way does not mean it is a good way for the animals to be moving in general. And if it is a style of movement that makes the horses more likely to have soundness issues (even if they’re bred for it, because all breeds are still subject to physics) then is that a thing we should be doing?
People ask the same questions about all other types of riding, so I think it is perfectly fair to apply it to WP also. But while you can go to the dressage forum and probably hear more than you ever wanted to know about the anatomy of the horse and how these parts move relative to those parts, so far the most we’ve gotten from a WP person is something that the spine of the horse isn’t actually supposed to be able to do, with the middle of the back being the highest point.
To be fair, there are many more people on the dressage forum, so perhaps that’s it?
(Though so far we’ve also been told that you can only be a good horseman if you show, and heard “look at all those other people who do awful things!” Which is… Not actually a good defense of your own practice. “Someone else is worse!” Is pretty much only a sensible sounding argument when you’re 8.)