Try to understand.
I didn't know if I accidentally triggered it while in the Crown Tundra. I was thinking that maybe I "encountered" it and it decided the nature before I even went after it. For the record, I think it was always Relaxed/Alert to Sounds the times I caught it.There's nothing special about Articuno's nature. Data reflects when a nature is truly fixed, and mine was not Relaxed. You may just be having an improbable but not impossible string of bad luck.
It doesn't matter too much because I Modest Minted it. It at least has perfect IVs in the right places. This was more out of curiosity.