This isn't just an indoor/outdoor comparison, it's a comparison or different medias and nutrients as well. To present the differences as solely due to light source is disingenuous.
IMO, their own conclusion debunks any findings:
In any case, the study isn’t designed to parse every variable involved in cultivation. It doesn’t measure differences in nutrients or soil bacteria between the “living soil” and the “artificial growth media.” It doesn’t bother with temperature and humidity. Nor does it compare light quality or timing — just “sunlight” versus “artificial light” — even though we know from other recent research at indoor grows that variations in light spectra alone can impact the production of both terpenes and cannabinoids.2,3 Furthermore, three of the authors represent companies that sell outdoor-grown cannabis or products made with it.
Yeah, this isn't science, it's marketing.