Wrong: there has always been another way. As an MVP and administrator giving advice on a forum I'm rather shocked you didn't know this as it's been around since at least Vista and still works with Windows 10.
Originally Posted by Brink
The way to 'hide' a user whilst still keeping the user picker logon screen working is to add a key in the registry and store the users there. True it involves editing the registry, and that not may be everyone's cup of tea, but it is not only a valid solution, it is the correct solution to the problem described.
The key in question is
The key names in red will need to be created. Once created, you can add the logon names as 32 Bit DWORD values.
The following is a RegKey file output that will hide a user called ThisLogonWillBeHidden.
The change happens instantly and does not require a reboot.
Windows Registry Editor Version 5.00