on a multi-user system not allowing you to choose the user to login in with, certainly eliminates anyone using the system for a total security win...

Then yes, it shouldn't be. It's a program bug. And to be honest, I've never had such a problem with SDDM (I use sddm-theme-maldives).

It is for security reasons. The login name is considered sensitive information.

I do believe he talks about the bug I faced as well whereby the ENTIRE login screen is white making it totally useless for the purpose. You can still type the password and login allowing you the chance to change the theme to fix it. And that must be one hell of a security feature on a multi-user system not allowing you to choose the user to login in with, certainly eliminates anyone using the system for a total security win...

At least it was one of them -debian pieces of junk that did it to me.

It is for security reasons. The login name is considered sensitive information.

I tried to install KDE's SDDM and it works, but it's all white, I can't see the usernames. This must not be happening?

I think it was the sddm-theme-debian-maui that did that to me, remove it and install the plain sddm-theme-maui to see if it gets rid of that foolishness. At least it was one of them -debian pieces of junk that did it to me.