Secret room under Primordius

I'm not sure if this is a secret or something, but last night while running ToT on LFR to farm Secrets, I got a glitch at the start of the fight on Primordius. At the start of the match, I fell through the floor and there's a spiral staircase underneath it that leads to a secret chamber - it didn't have anything in it, but when I entered the room, a text header appeared on my UI that said something like "11 attempts remaining".

Is this something that players see in non-lfr content, or did I just stumble upon something that just never got fully implimented?