The final court document does not seem to conform to your argument. Section 13 for example, does conform to your points. It states that "By purporting to be able to perform engineering services or work, Jarlstrom engaged in the practice of engineering...".
However, section 14 is very different. It does not rely on his use of the title of engineer. Instead it states "By reviewing, critiquing, and altering an engineered ITE formula, and submitting the critique and calculations for his modified version of the ITE formula to members of the public for consideration and modification of Beaverton, Oregon's and "worldwide" traffic signals... Jarlstrom applied special knowledge of the mathematical, physical and engineering sciences to such create work as investigation, evaluation, and design in connection with public equipment, processes, and works. Jarlstrom thereby engaged in the practice of engineering under ORS 672.005(1)(b). (...) By engaging in the practice of engineering (specifically, traffic engineering) without registration, Jarlstrom violated ORS 672.020(1), and OAR 820-010-0730(3)(c) on a second occasion."
Section 14 never cites the use of the title "engineer" as relevant for violating ORS 672.020(1), only his engaging in the "practice of engineering." As a practical matter, they may not have brought legal action if he had not used the title, but they certainly believe the law states that disseminating his findings certainly count as "practicing engineering" and is illegal without certification.
Actually, I wonder if the court didn't misinterpret 672.005(1)(b). I've cited it below and it seems to rely on the work in question being used for the purpose of ensuring compliance.
672.005(1) states: "Practice of engineering" or "practice of professional engineering" means doing any of the following:
(b) Applying special knowledge of the mathematical, physical and engineering sciences to such professional services or creative work as consultation, investigation, testimony, evaluation, planning, design and services during construction, manufacture or fabrication for the purpose of ensuring compliance with specifications and design, in connection with any public or private utilities, structures, buildings, machines, equipment, processes, works or projects.