RNG will always be RNG, so just because you get your Atma drops outside of these time periods doesn't mean that they're necessarily wrong. I was skeptical about the Atma theory at first too, but since then SE has released S-rank hunts with rather unique and obscure ways of spawning them. I wouldn't be surprised if there was some bit of truth to the Atma theory considering that history. Unfortunately it won't guarantee drops either, and this game's RNG seems to be particularly cruel at times (Failing a 94% chance to meld 6 times, failing to get a HQ item with over 90% quality consistently, and the chance of getting A High Wind in Ishgard for your Ixal Dailies).