That seems really weird. How do you hold anyone accountable then? How do you know who was logged in last as the only admin? What do you do if someone were to change the admin password and not share it? Or if someone gets hacked and they take over the admin account?
That’s a lot of risk with little reward.
I could support this feature if it used the “use real names” setting in the Admin area. If that setting isn’t set, then the username should remain present.
As an aside, I think this should be two separate requests, as the need for them do not align with each other and obviously a lot of discussion could be had on how you setup your admin account…