The confusion is there only because there is no official Chinese localization. The majority of localization decisions in imink is determined by the official Japanese counterparts. In the Japanese version, the game rules are prefixed by "ガチ" which means "Ranked" or "真格". Your preferable translation may be more similar to the North American version, but we in imink tend to follow the practice of Japanese version, which is more to the original minds of the creators of Splatoon, without the second-hand interpretation of the North American version.