Unable to view Vanilla and TBC dungeon maps

Could you please explain why I am unable to view dungeon maps from the Vanilla (Classic) and TBC (The Burning Crusade) eras in Onyxia Realm?

I used to be able to view these maps normally during those expansions.

Now, however, I cannot view them at all, whether I am inside or outside the dungeons. Is this a bug? If so, could you please look into fixing it ?

Don't you need to use something like Atlas addon for that? I think you can see old instance maps naturaly only after Cataclysm. (As far as I can remember anyway. Been like 13 years since I logged in to a Cata server.)

https://forum.warmane.com/showthread.php?t=424250

Because they didn't exist.