Technically golden retrievers are one of those breeds that are expected to be breed standard height whenever shown.
Just like they should have a scissors bite.
These are the only disqualifications for the breed.
Judges generally are more lenient - especially with 6-9 month puppies and I had an all breed judge assure me that they are not even looking too closely at bites with pups because they are still growing. My question was not on the correct bites or size, but she covered those areas as well in answer to my question.
But a stickler judge could DQ a dog who is not qualifying. And there's politics.
My Bertie comes from slow-grow type lines (I think). I have not spoken with his breeder on this, but I noticed she typically shows the dogs more after 9-12 months. I don't think she brings them out as puppies. I could be totally wrong.
Him, he could not have been shown as a 6 month old. H-e was too short.
He wasn't full height until after 12 months. I want to say that by 12 months, he was still about 19-20" tall. I showed him the first time as a 14 month old and he was about 22.5 to 23". He always looked very small compared to some of the other dogs. Even when we started showing in the Open class, he was still filling out and I had to ask around for tips on making him look as big as the other dogs we were competing against.
He has been pretty much in the 68-74 pound range quite a bit most of his life... but I know his one brother who was like his twin is 80 pounds (gave me a shock to hear because he doesn't look it).
Because this is a sporty breed - they don't want the dogs looking like labs out there. There's a lot of focus on movement - especially breeder judges (looking for correct movement) and all breed judges (looking for correct plus a little extra pizzazz movement).
ETA - my puppy is about 23.5" and weighs 65#. If he gets any taller - maybe figure 1/2 to 1". Some dogs grow differently than others. For example with Bertie and that one brother I mentioned above - his brother a couple inches taller than Bertie at 9-12 months and worrying his owner, but it all evened out in the end with the boys being the same size.