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.)
Some legal background:
One would think that disagreement between Circuits about the meaning of a law would be legally relevant evidence about whether the law was ambiguous. Instead, there appears to be a circuit split on the meaning of circuit splits.
More available here, for the amusement of those on this site who like to think meta. Also a bit of a lesson on the limits of meta-style analysis in solving actual problems.