You’re right, but @slawa and I have already got Chunghwa to use our APRC numbers for this (after some arguing).
Actually though, I’m not sure whether that completely fixed the problem. I’ve previously fumbled my way through registering for NHI online services (before forcing Chunghwa to use my APRC number rather than passport number) and MyData (after doing so), but I did have some issues with the verification process during the latter. I’m not exactly sure what the issues were from the vague Chinese error messages and descriptions of the various verification possibilities and just trying to complete the process as quickly as possible while being frustrated.
Is there a convenient way for me to check if this verification process works for me? (Note I don’t have an employer here, so I’m probably not registered with the pension system or anything anyway.)