Interesting, since it didn’t happen!
Actually, virtually all "creation scientists" say it DID happen. The "horse kind" (Family Equidae) is the single most commonly cited example of a "baramin" or "originally created 'kind'."
IOW, creationists DO accept the common ancestry of all equids. (At most casting off only the earliest members of the group.) Apparently, however, their lay followers don't pick up on this.