It's only one game, this is Definitive edtion (improved graphics and overhaul + DLC content from original version), older version had base game and DLCs
I mean, it's not Collection but different edition/version

That's fine.

It's a 'different' game with a different place in your steam library. This was patched and remaster for the new gen consoles and it's basically the same game on PC but with different light effects and some better textures (for some they are worst). DLCs are already included in this version, is "complete version" more than a remaster.

I'm not the GA creator so it's not up to me, however, as huakeavaeja said, it's only one game.