>It is too young from a responsible breeders view point though,
Yes it is. I have a breed that is sexually mature at 6 months, and I have certainly heard of litters sired by youngsters. But you have to take into account if it is worth risking the loss of a potential good stud dog. Most males still have maturing to do mentally, and it would only need a dominant bitch to turn, and she could totally put the dog off for life.
People assume that all males will copulate willy nilly (pun intended) but it isn't so. I knew of one owner who was always telling her boy off for humping his teddy. When he was old enough for her to want to use him, he wouldn't perform!
I do like my boys to be confident little chappies in other ways prior to proving them. And yes I agree that proven means the bitch is pregnant. I wouldn't call a dog proven just because he had actually achieved a tie. And at 6 months, you can't be sure that a male is going to be suitable as a sire (well not in my breed), as there is so much more improving to do coatwise.