Here’s my “insight”:
I go to the Steam store page
... and you don't blame steam for not updating information in their own app?
Of course I don’t. It’s the developer/publisher who manages the content on their pages using Steamworks and it’s their responsibility to ensure that it’s accurate.
https://partner.steamgames.com/doc/gettingstartedValve don’t write the descriptions, upload images and videos, manage DLC etc for every game on the site. There’s over 50000 of them. It just wouldn’t work.
You seem very keen to absolve Larian of all responsibility for this.