My QH gelding does this, and he's about 14-2 (e.g. Not tall, and definitely not long-legged!) His half-sister and her daughter do it, too. I wondered if their dam did it when she was younger.... I have her now and she doesn't do it, but she has so much arthritis in her front end (at age 31) that she wouldn't/couldn't hold her feet up like that now.