I'm not saying that there isn't a choice. I'm also not saying whether a treasurer should or should not be appointed. I'm saying that I've never seen it written that the treasurer MUST be appointed, and so I have no reason to assume that such a rule exists.
Maybe the board is, by your reasoning, foolish to the extreme. Maybe it is not.
Well, http://wikimediafoundation.org/wiki/Treasurer_Search says "appoint" and makes no mention of it being only until an election and there is no reason to assume they plan to put it to a vote, so I'm going to give them the benefit of the minuscule amount of doubt and assume they are not foolish to the extreme.