The very successful HUS horses are not western horses in english tack. That might be seen on a local level, but at shows like the World show and the Congress, its not the case. The finalists and high placers from my experience, have had huge, flowy, sweeping strides, level headset, even top-line. I'm sorry, but the picture you posted isn't working on my computer for some reason, but like I have said, they generally just look for a nice stride and an even top-line, and most of all, consistency. With the HUS, it really is based entirely on the judges opinion. Some like a shorter stride, others a larger one, and I have even seen judges that actually like the more huntery look (IE: My horse. Definitely not successful HUS material haha!). I am good friends with a girl who has been very successful in the HUS on a national level and is extremely known, and literally wins every time she steps into the arena. Her horse is about 16.1 but his stride is HUGE, flat, and he's the same every time you look at him. The way you ride in the under saddle is not judged.
This is just my opinion on what I have seen while showing on the QH circuit. :)
I know this is pleasure driving, but the horse that is being videoed is probably one of the most successful hunter under saddle horses in AQHA history. He has also been extremely successful in the over fence events on a national level.
Just my opinion on the ideal under saddle horse :)