Exactly. If "high elves" were introduced for the Allianced, they wouldn't have a "shared starting zone experience" with the Horde's blood elves and then decide if you go Horde or Alliance. They'd start AS Alliance already, from the get-go, just like all the other Alliance races. Except for Pandaren, of course.
Which is why I keep insisting that the idea that the Thalassian elves would somehow become "neutral" if high elves were added as a playable race for the Alliance is nonsensical.