The purpose of the whole "keeping the knowledge of other worlds a secret" is to prevent people like Xehanort and Maleficent from spreading chaos, but as a whole the concept never had much purpose. Basically, it was a way to keep the devious people contained to their own worlds, which seemed to work for a while, the average Joe couldn't do anything with that information anyway and the protagonists break that rule constantly because it's just more inconvenient than anything. Ironically, Days and Organization XIII is where that best use of the rule was implemented since stealth and sneaking around was key, but it had nothing to do with preserving world order.
On top of that, most of the worlds they visit are strange and fantastical in their own right so I don't think anyone would bat an eyelash at visitors from another world, especially since the universe has had a strange influx of monsters lately. When a world is crawling with pitch black monsters from Hell stealing and devouring their hearts to multiply and threatening to destroy the planet and all the inhabitants but they're being stopped by anthropomorphic animals that can talk and cast magic, and a funky looking spiky haired kid with an enormous key, I think where they come from is the least of the worlds' inhabitants problems.
All in all...yeah, it was kind of pointless.