A discussion page exists[0], but the review page is empty when you view it (and clicking to add a post brings me to the TF2 review page!)
Enhanced Edition is on Steam, but you get it when buying the original Metro Exodus. You get both, the original game (steamid 412020) and the Enhanced Edition (steamid 1449560) in your steam library.
I don't own it, but from reading OP's post and other stories online I'm guessing it's similar to how the Call of Duty games handle Singleplayer and Multiplayer. They are 2 separate "games" in your library that you get from a single purchase, and can install independently. But from what I can tell in steamdb, the CoD games don't seem to use separate steamid's for the split, while Metro Exodus EE does.
https://steamcommunity.com/app/1449560/discussions/