I can understand why you think so... and considering the character of Gaara's sand logically fits an Earth+Wind KKG, I wonder why Kishi didn't just use KKG to explain away his dubious abilities? There hasn't been any solid evidence thus far that points to either:
i) the source of Gaara's abilities (His mom just makes the sand intuitively protect him; I don't think it is the source of his ability per se)
ii) if Gaara is theoretically and/or virtually the only one who can use it! If it is (as some claim) the case that Gaara infuses wind chakra into his sand to control it, then i suppose every wind user would be able to wield sand jutsu just fine?