Forfeiture v. Sound Analysis

Here's footnote 5 of an opinion published here, issued after a rehearing petition in an anti-SLAPP appeal:

This issue of first impression was first raised in defendants’ petition for rehearing. Ordinarily we might treat it as forfeited, but having certified our opinion for publication we could hardly refuse to address a point that, if sound, would undermine our entire analysis.

Waiver: Not gonna go there.
Logic: We gotta go there.