The words themselves do not necessarily mean that the person administering the rite believes in the Trinity.
For example, both Jehovah's Witnesses and the Mormons use that formula. The reason, of course, is because, like Christians, they use the wording Christ commanded in the Gospel according to St. Matthew. However, since they do not believe in the dogma of the Blessed Trinity, then their baptisms, although utilizing the correct wording, are invalid because the Trinity isn't being invoked...because it cannot be invoked by those who reject It.
That is what OrthodoxyUSA is getting at. And he's absolutely 110% right.