That sounds plausible. According to the myth about Kyurem in Lacunosa, it "arrived on a meteor," and it's just been sitting in Giant Chasm, threatening to capture and devour any townsfolk wandering around at night. This myth isn't too reliable right now, so I'm less inclined to believe it's been in Giant Chasm all this time. I think it's more likely that Kyurem been in more than one location.