My gripe is that, if some additional authentication is then not required for deployments or SSH access, that whoever has access to the admin UI will still be able to access the box and extract all secrets, just with extra steps. There's usually no real security boundary between "admin UI controls the box" and "box requires secrets in plain text".

I still like the approach, but I'm afraid that it feels more secure than it is, and people should be aware of that.