This is pretty classic Apple: hide useful information, expose it to power users who discover it.
To be fair, on macOS, it’s a longstanding tradition that if you want to see more complicated stuff (in menus, in apps) hold down option.
But yes, it’s not discoverable.
Though I am also struggling to know how I would know that had you not told me. I don't see it in the menu bar nor on the support page[0].
[0] https://support.apple.com/guide/contacts/keyboard-shortcuts-...