One of my family's first chickens was an Easter-egger from Tractor Supply with short legs like this. I don't remember if she was 'shaggy' like your girl, but her back was definitely a good couple inches below her sisters of the same breed when standing at full height. She lived to be about 9 years old if I remember right, and didn't slow down until the very end, so obviously she wasn't too bothered by her stature differences. I recognize some facial structure quirks on your bird that are similar to what mine looked like, like a sort of shortened beak and the way the eyes are set on the face. It's possible it's genetic, but I never really hatched anything until long after my bird was gone, so I couldn't tell you if her uniqueness would be passed on or not. Just thought it was interesting to see another like her, and thought you'd be interested to know she wasn't the only one! 
