I agree that's likely the case, but if people are getting their hopes up over one site (that I've never even heard of) with no sources given and no coroboration from any other media outlet, I'd say they're setting themselves up for a big let down. The whole story screams either outright bull to me, or at least a misunderstanding of the fact that the entire FFXIII project as a whole isn't exclusive which was never a secret to begin with.
And I'd like to see some of these interviews you mention indicating Square was considering porting FFXIII to the 360. I've certainly seen them mention supporting it as well as the Wii, and not just the PS3 this gen, but I've never seen anyone at Square mention that they were even considering an FFXIII port.