Because golden is like blood bay, mahogany bay, Chestnuts, etc in that they have various types of the base coat color and all of them get rerolled off the horses and change to something else with that colour
:O i had a golden dunskin rabicano horse and i did an reroll to see if i could get rid of her socks why did it make her a normal dunskin??? i so sad now :(((( she went from 1/15 to 1/215