The user who was logged out also issued the sleep orders, directly or indirectly through their configuration options.
When the computer is woken up, it knows that the account was what put it to sleep. So, only that account should be able to return it from sleep.
Unless I'm missing something, that's working as intended. They'll have to log out for you to log in.
Now, you could probably use CTRL + ALT + F3, log into the TTY, and start the desktop from that newly logged-in user.
In many cases, it's just startx to start that user's GUI desktop. However, we now have Wayland, and you'd need a different command to start the desktop up.
Also, after it has started the desktop (in that instance), you may need to hold down the left Alt button while pressing the right arrow button. That'll scroll you through the TTY options until you get to the one where there is a GUI desktop session.
