I think it just means that Iridikron in drake form is unlikely to be a boss, or at least REGULAR Iridikron. A future fight could be corrupted Iridikron (decay version) or he's in visage form.
However I do think it lessens the chances of him being the final boss overall. Murozond, Vyranoth or a dark horse are all possible (or Galakrond still lol).
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Iechrom would've been cooler but it's probably silly sounding because she is silly.