What I did: opened the pause screen and left the hypixel server running while in AFK (the server is not important, but it's easier to replicate that way) and then joined my survival world (singleplayer) and the title that was still being displayed. 

Furthermore, it doesn't seem to tine out like it does on the actual afk server, and persisted after reentering the world (without closing the game window).

Closing the window and reopening the game made it go away.

I have done some experimentation and it seems as though it works in any LAN world/server that does not stop when you enter the game menu. The recording of what I did to replicate it is also attached. I did not manage to force it to display the title forever, as it did before, though.