Hi , I'm James DVM MRCVS and would like to help you with your question
your breeder might be right .
I have come across Vizsla puppies which only later have developed their more coarse hair .
I would not judge them right now especially as we are not dealing with one pup showing this character but several.
More over - if this is a respectable breeder , she will not risk her name and reputation on such a thing
I hope this helps you and your decision making
If you have any further questions please ask
all the best to you and your new member of the family.