The possibly don't list Ecogard on that group because afaik Ecogard is already directly under and controlled by Premium Guard so they just list PG there where as all the others in that list are seperate entities : https://premiumguard.com/portfolio/ecogard/
While PGI may be the parent, Ecogard seems to almost be its own thing with construction methods that differ somewhat than most run of the mill PGI filters and the private label brands they make for others.