There is a difference between an account on the app and an account with Princess Cruises. DH is allergic to technology, and I have always done the registrations, etc. He does not have a separate login for the web site, but he does have a Captain's Circle number and gets all the loyalty benefits he's entitled to. He definitely does not have an app login. He appears on my app account as my travel companion, and he's fine with that. It is not necessary to have separate logins on any device in order to manage a cruise for both of you.
(DH mourns the old days when the much anticipated cruise docs showed up in the mail.)🙂