Menorah-dic Chanukiyos

The Shulchan Aruch OCh 673:1 (citing the Tur b'shem Rabbeinu Yerucham) states that some have the practice to add an extra candle next to the neiros chanukah so that if he uses the resultant light, he will be using the light of the extra candle, rather than the light of the neiros chanukah which are prohibited to derive benefit from (As long as there's one source of light, additional sources of light are not considered to add additional benefit - the same reason that one is allowed to benefit from a light that a non-Jew turned on on Shabbos in a room that already had at least a small source of light inside it, while if the room had previously been entirely dark, the new light is prohibited to benefit from, even if the non-Jew turned it on - for the Jew's benefit - of his own volition). The Rema notes that we use the Shamash, which we had previously used to light the other neiros, for this purpose - which has the additional benefit of more obviously not being an extra candle of the mitzvah.

The Shulchan Aruch continues that this extra candle should be slightly distanced from the other candles. The Levush and Gra (cited in the Mishnah Brurah) explain that the reason is so that it is clear how many candles are being used for the mitzvah of that night, while Mahari Weil (ibid.) gives an addition reason that it is so that if he wants to use the light, it will be clear that he's using the light of the extra candle, rather than one of the candles of the mitzvah.

This being the case, I don't understand the fascination with using chanukiyos that look like polydactyl menoros. If the extra candle is in the middle of the other candles, how is one to distinguish between them? Granted, if the central lamp of the menorah is much higher than those of the branches, I can see that this may be enough of a distinction (the Rema quotes the Mordechai saying that this is a good idea, at any rate, so that he will specifically use that candle for his personal needs), but in most of the pseudomenoric chanukiyos that I've seen, the center lamp is raised up over the other lamps by less than 1 cm. Perhaps the fact that the extra candle was used as the shamash is enough of a distinction, as per the previously cited Rema, being that when he lit the candles, the right number was in place? Tzarich iyyun.