You don’t know that. It has never been said in game, hinted at in game, or implied in game. You are assuming it perhaps because of youtube content creators that make up speculations as such. But the game has never confirmed any normal geography which is being obscured anywhere.
Yep. That is why I am forced to include another universe being one of my possibilities. Especially since we have the precedent of them having us link our planet to another universe in Warlords of Draenor. If they did it already, they could do it again. Or… here is just some pure speculation. What if the act of linking alternate Draenor of 35 years ago to our Azeroth of our present… unfortunately also put a bit of a magical link from that universe’s Azeroth (to avoid confusion…the Azeroth which would exist in the universe where we killed Ner’zhul and stopped Gul’Dan) to our Azeroth of 35 years ago in our timeline? Notice, since we stopped Gul’Dan and killed Ner’zhul…there was never a horde invasion of that Azeroth, never a Lich King, never a destruction of the Sunwell, never a separation or division between the Humans and High Elves. So what if that Alternate Azeroth had an even stronger bond between Humans and High Elves…so much so that they interbred more readily and already had a Light Emperor that was receiving prophecies from the Naaru? Now, we saw in our own timeline that the Nathrezim were feeding fake prophecies to Naaru as a long con to get rid of those Naaru…but since there wasn’t a Legion invasion of that Azeroth, maybe the Nathrezim in that universe were feeding fake prophecies to those Naaru to get rid of them. And so maybe that prophecy assumed the Naaru needed to travel with the expedition that the Emperor sent…and despite their prophecy, the Nathrezim could have arranged it so their expedition failed and the Naaru would accidentally zap through the magical link between our worlds and find themselves injured or incapacitated underground in a different universe. Unable to oppose whatever the Nathrezim were planning back in their alternate universe. That might also explain why all the mages of the expedition were killed. The Nathrezim didn’t want them to be able to come back? So yes, the Light Emperor would exist, but “not” on our own planet at all.
Wasn’t that the entire premise for the mag’har recruitment scenario…? That the bronze flight noticed a strange magical link from their AU Draenor to our Azeroth?
The character Faerin Lothar mentions that they have a Light Emperor that sent her expedition in the beta. She talks about him with Anduin. She does “not” give enough details to exclude any of the options I mention in my original post, though.