Uphill or downhill is not actually determined by whether the croup is higher than the wither... While EVERY horse with a croup higher than the wither IS downhill, even horses with higher withers can be downhill in balance.
To find levelness you look for the LS joint (or in a photo we can usually use the point of hip as it will give us a good idea, if you can get hands on a horse then feel for it, it will be the soft spot along the spine just before the point of croup, you can learn to see it in photos with practice) and the lower cervical curve (the lower curve of the neck - also the widest part of the neck)
You draw a line from those two points and it will show you how level, downhill or uphill the horse is.
I like the overall package of this little horse, he's neat and tidy, definitely cute, but not specifically as a dressage/jumper project... As an all around general riding buddy I'd be smitten though.