Note the comment by "Jurist of Reason" on that article:

If you google the cites, you can quickly find that neither the 11th or 4th Circuits were talking about Chevron deference (in both cases, the issue was the interpretation of 28 USC 1367, the supplemental jurisdiction statute), and neither actually said that the existence of a circuit split could never be considered in evaluating ambiguity. Rather, they rejected, in passing, suggestions that a disagreement among circuits about the meaning of a statute automatically makes it ambiguous, instead finding that each court had a duty to make its own determination. This seems pretty unexceptional to me.

(To be more specific, the non-admin context matters because these courts had to actually decide what a statute meant, they couldn't just punt and say that it was "ambiguous" and so an agency decision was reasonable.)