I believe this just means that you have to submit your app as an organisation developer account, not individual developer account. This will require you to submit all required information to that effect, particularly, DUNS, which globally identifies business entities. In some other cases you may be required to also submit other information in some areas such as legal accreditations / other regulatory information if you're in a regulated industry such as healthcare, financial services, or gambling (as mentioned above) these should also be provided during the sign up process.

As this is outside the app, I understand it is authorised. If we are interpreting 5.1.1(x) literally as written, it would be authorised but you won't have the email address to recover the password with. so the question is "how do we define a core functionality and prove it requires ID" ? And whether 5.1.1.(v) supersedes 5.1.1.(x) Yes that's is probably the key question - does 5.1.1(x) only covers "non core functionalities"? And is "password recovery" a "core functionality"? Have not contacted support yet. I thought Apple Developer Forums would be the correct place to ask these questions first. But I can see that it's kinda quiet here :D So I'll shoot them a message I guess.

Going to https://developer.apple.com/contact/request/unlisted-app/ gives me the following Sorry, you cannot view this page. The Apple ID you signed in with does not have permission to view this page. If you’re currently a member of the Apple Developer Program, you or your Account Holder may need to update your account by agreeing to the latest license agreement in order to access this page. To view your current membership status and benefits, visit your account. Any help appreciated.