What determines the visibility of incumbent succession plan? Shouldn't HR be able to see all Plans?

Summary:

For our client, some other vendor had earlier implemented Succession Planning. Their contract ended on not-so-good terms and we replaced them. The client says that some succession plans were created that we can't see as HR Admins.

I know a superuser can be created to see them but my question is isn't any succession plan (incumbent type) visible to HR specialists by default?

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