Grandad kept a horse once till he was a 3 yo before he was sold as he needed time the horse went on to win an Inter had he been sold as a yearling he would have lost his head long before his 3rd birthday
and i think a lot of the time extra time will pay off for a lot of horses i agree with you if the trainer thinks the horse will only win 1 race though you get rid of it with the import fee being 5k for colt's it is good it may help the breeder get that bit extra for a yearling instead of only not much more than the service fee