I think it's right for a breeder to narrow down the pup's for a buyer, once they have the full information about the buyer and what they are looking fr from their dog.
No visitor could know the full character of a pup from a half hour visit, where as a careful breeder pays attention to the litter picks out the bold lively pup's and the quieter ones.
it's also about getting the closest match as you want your puppy owners to be happy long term, it's no good sending the lively pup to a home thats neber had a shepherd before no matter how many there parents had

We do this with all of ours.
The other breeders is probably just looking for sales if they keep pushing, something should catch your eye make you want to look further talk to them meet the adults, both where possible

good luck with your search