Why should they? Aparently they coudn´t get pure bred horses. But still wanted to exhibit them, as a prime example of endangered/extinct chinese native species. So they serve as ambassadors with a strong message to general public, I guess, and everbody is happy. I don´t think many visitors spot the difference between hybrids and pure breds. (Anyway, there are no 100% pure Przewalskis anymore on this world, so.)