chatting to horse box builder the idea is that rather than having something that comes part easily when the idiots/ little darlings do climb into / onto things they shouldn't - this stops them doing it in the first place - so then the breast bar is sold and structural and makes the lorry stronger in itself.
I've only watched the first minute or so of that video, but I see a frightened young horse travelling solo who is tied up much too loosely and has no haynet to munch. He's trying to turn round and is also considering jumping over the breastbar. He's not leaning on it for support as such.
He's bothered by the moving scenery that he can see out of the side window.
I rang them and after a discussion they decided my van wasn’t strong enough. It has a removable bar and a large grooms door.
I solved my problem by fitting plain curtains to the side windows and a homemade ‘sail’ to block the rear view. There haven’t been any problems in 3 years.