>>53176474He’s pulling it out of his ass in saying that all of them fit the pattern, but many box legendaries duos do have a male and female leaning member each.
Gen 2 has Ho-oh (fenghuang/houou) and Lugia (dragon), historically a female and male duo respectively.
Gen 3 has Groudon (clearly masculine) and Kyogre (referred to as feminine in SWSH).
Gen 5 has Reshiram and Zekrom, who are explicitly referred to as feminine and masculine by Sugimori, respectively.
Gen 7 has Solgaleo and Lunala, the masculine and feminine evolutions of Cosmog who need to join (breed) to make another.
Gen 8 has Zacian who is referred to as the “sister” and Zamazenta who has the mane of a male wolf.