Stable isotopes (C13, N15), as discussed in the article, are entirely different from radioactive isotopes (C14, etc.).
The study that used extreme cooling dealt with alpha decay, not beta or gamma decay. Also, cooling of that magnitude is not likely to occur naturally on earth.
Given this, I don't think this study has any implications for radiometric dating.
The implications of the earlier article remain. Would you like to explain the decay mechanism to me?