Makes sense to me as with any animal in RL they very from climate to climate and region to region

I imagine a merchant going to the desert to buy a particular stallion and return home to sell the horse seed to breeders. Horses could be fast and thin in the desert, heavier in the north and able to carry more loads etc .... Breeders could create stud farms with specific breeds .... others could test crosses. And horse dealer would become a very interesting job !

They mentioned that there will be... You will get a voucher for a horse and will be able to go to a breeder in your area and claim a horse from their sock.

it is not very clear. A horse ... but what kind of horse, for example.

They had the livestock starter kit for sale in the promo. They've also had the prized livestock kit for sale in prior promos. They also have a pets & mounts category which lists a variety of animals including a purebred horse and mule. And we've seen the dryas elk show up in the store as a brudvir mount as well as the basilisk lizard in the current promo, confirming that there will in fact be biome specific mounts.

So I'm sure we will see more variety as they add more content to the game/store.