And is it possible that the eggs he is selling are not from his best hens and those are just for a show?
Of course anything is possible. Some people are just more honest than others. Some people are more knowledgeable than others. Do you know if they are showing birds they hatched? If they are, how do they do in competition? There are a lot of different possible explanations, some good, some bad. I don't know how much of this you already know.
Even the best breeders hatch a high percentage of defective birds from their best breeding birds. I regularly hear 80% to 90% of the chicks hatched will have some flaw that will keep them from winning a prize. I don' know how bad the flaws were on the birds you hatched. The majority of those flaws should not be that bad, many should be pretty close to perfect but with something minor to prevent them from being true show quality.
You mention pictures of the hens. Do they show picture of the fathers also? They are both important. And yes, they will show pictures of their best.
Different breeders use different systems to maintain genetic diversity once their line is established. Spiral breeding is a typical one but there are others. They don't breed the same males to the same females every year but systematically rotate the best male from a certain group to the best female from another group. Since these matches change every year they haven't raised chicks from that specific match before so you can get some surprises. The longer these lines have been established thought the fewer big surprises you should get.
It takes a lot of knowledge to know which male to match with which female to get the best offspring. Some breeders can handle this better than others. They have more knowledge or care more. Over here some people get hatchery quality birds and breed them, selling them a purebred birds with no real regard for the SOP requirements. I don't have a problem with that as long as they let you know what they are doing. At the prices you are paying I'd expect better, but I don't know the market in Poland.
How do your goals align with the goals of that breeder? Different breeders select for different traits. You may assume they are breeding for show quality when they are really breeding for the mass market. Have you tried talking to them about what you want and what you got?
I don't know what your options are in Poland to meet your goals. Since Poland is a member of the EU how hard would ti be to find other hatching eggs or even better, older birds in other countries?