What happens when adding a game from a third party to Steam library that Steam also sells?

[Aeternuslee]

Odd question and if this is posted in the wrong form please let me know.

I was wondering if anyone knows what happens when I add a game to Steam (Games > Add non-steam game) that Steam sells but I did buy from steam?

Two examples
Ex 1: I bought worldbox a few years ago when you had to download it from the publishers site as an small .exe file. I notice steam now sells it so I added it to steam a few weeks ago.

From what I can tell Steam is now treating it as if I bought the game from Steam. I can uninstall and reinstall directly from steam.

Ex 2: I own Against the Storm (City builder) on epic games in its early access branch and it is coming to steam in 2022 Q4. Personal preference wise I would rather own the game through Steam as I have always had issues with Epic Launcher just not working half the time.

What would happen if I add this game to Steam. Will I be able to install, update and manage mods through Steam or would I need to buy a second copy of the game from Steam?

[Cheezus Crisp]

No. You lose ALL community features of a game when adding it this way. Adding third-party games is nothing more than a shortcut and a way to show your friends what you're playing. Nothing more.

[Aeternuslee]

Thanks. I thought that would be the answer but a man can always hope.
Wont be the most expensive game ($20) I have bought more then one copy of for asinine or esoteric reasons then. :)