This is somewhat true. I will say a 3rd possibility is the foal that just hits the ugly duckling stage faster than normal. I had a colt once that was spectacular for the first 3 weeks…and then it just went down hill LOL like refused to move at all at his inspection, was not even photogenic for a few months. I knew he was quality but could not for the life of me get anything useful as far as advertising materials. So I left a sale ad up but didn’t really promote him. Someone contacted me when he was a yearling and I forlornly went to get video and then BOOM that quality I knew was there actually showed up that day.
As a small breeder my goal is to sell them before weaning, sometimes even in utero, unless I plan to keep the foal for myself