There's nothing wrong with someone saying 'I'm the architect' - if that's what they really are. That said, it might be a power thing.

Now - there's more wrong in saying 'I'm an architect' - because architect really is not a profession, really. I suppose you could kind of get away with saying that if you have a lot of experience, and have been in the role of architect for some time, but it's a difficult thing to say and strains credibility if you were to put it on a resume.