It would be logical to conclude that the Titan dungeon assets were re-purposed for the Kobold stronghold once they had decided Titan was no longer going to be a part of the pre-apocalypse game.

We saw the same thing happen as assets from across the future Coerthas, Twelveswood and Thanalan dungeons were re-purposed to piece together the Aurum Vale, Dzemael Darkhold, the Thousand Maws of Toto-Rak and cutters cry.

So I wouldn't consider the appearance of the U'ghomoro mines as highly significant, other than to show what Titan's domain would have looked like.