What does the login screen have to do with mobile? They’ve had them since at least Windows 95 (I forget if 3.1 had one), and they’ve been evolving every release.

If you mean the screen before the login, that’s been around since at least Windows 95 too, though it didn’t used to be default and required you to press Ctrl+alt+del to dismiss (which before win95 would reboot your computer)