Instead of “being suspicious” of a Reliable Kashrus Organization (just because you do not understand their logic), perhaps, you should simple ACCESS the article (which is available on the cRc Web site). The specific article is in the January 2012 Issue of “Sapirim”. In the article, the author explains that NORMALLY a Cast Iron Pot *will* require “real” libun (i.e., put it into a self-cleaning oven). However, the SPECIFIC case of “seasoning” where NO OTHER non-Kosher product was involved in an “exceptional” case. Citing a disagreement among the Achronim here, the author notes that in this SPECIFIC case, the Shach and R. Akiva Eiger are strict and require “real” Libun. However, the Rema, Magen Avraham, and Chasam Sofer rule that Hag’ala is sufficient and apparently, there is a consensus among Poskim to be lenient in this very specific case — where the liquid that was “cooked” in the Cast Iron was — itself — non-kosher — that Hag’ala is sufficient.
The author is careful to point out that this is an EXCEPTIONAL case and that in the “normal” case of kashering Cast Iron, you would need “real” libun.