I'd assume there's a drop-down menu with a list of breeds, that the person didn't notice or couldn't find "coloured cob" on and the 'default' would be akhal-teke
betcha that the submission form for the advert had akhal teke as the first item in the list, and the advertiser either just didn;t change it or there was no list entry for 'cob'.
Sorry - computer programmer going for the obvious here.