You are correct that the judge ruled the stop was "justified at its inception"; but the section immediately following your quote is titled

> Alaniz did not Have Reasonable Suspicion to Extend the Traffic Stop.

That's the newsworthy part. For example, Kyle stated that she had the marijuana only after Alaniz detained her so that he could attempt to search the car without her consent. If that detention was illegal then her statement isn't admissible, and that's what the judge ruled here:

> Because the government does not identify any adequate exception to the exclusionary rule, all evidence obtained after Alaniz initiated the ALPR search must be suppressed as fruit of the poisonous tree.

ETA: And while the initial stop was lawful, the grandparent comment is probably correct that it wouldn't have happened without Flock. Alaniz performed a Flock search that included "traffic violation" as the reason, but he hadn't yet observed a traffic violation at that time. Based on that ALPR history he correctly suspected drug trafficking, and followed the car until he observed a traffic violation that justified the stop (but not the subsequent fishing expedition).