I was just thinking about this in relation to my own Pony, who was a stud pony until he was gelded at age five, at which point he was started. I was just wondering, would you want the services of a stud horse / pony that had not been ridden? If you were going to pay for someone to impregnate your mare, wouldn't you want to know how they moved and acted under saddle? Or does it not really matter? I'm just curious.