The Przewalski’s horse is not the wild form of our horse. It’s a other sub species (a little bit like the zebra or the donkey) with (for example) another chromosome count. Another problem is that there are evidences that the modern Przewalski’s horse feraled from a domesticate form of the primal Przewalski’s horse (that was tamed by the Botai culture). A further problem is that the Przewalski’s horse was extincted in the wild for decades and only survived because of human breeding (so it was kind of tamed again).