In the UK it is completly different. THe Show hack is between 148cm's and 160cm's is fine boned and elegant. They are a perticular type. Hacks
If the horse has more bone than a hack or is over height then it becomes a riding horse. Riding Horses
If the horse has more bone and substand then a riding horse it becomes a hunter.
Non of the above can be ponies and nothing to do with whether it hacks out or not. A horse is one type, it cannot be both a hack and a riding horse and it certainly can't be both a hack and a hunter