Good day Sam.
OK, we agree then, there is no certification requirement in ISO 45001. I probably misunderstood your phrase "ISO 45001 also indicates Requirements" (english is not my native language). I thought it referred to a certification requirement especially.
Also, like any other certifiable standard the ISO 45001 also indicates "Requirements". Under introduction 0.5 contents of this document clearly indicates "seeking certification/registration of its OH&S management system by an external organization".