If I remember correctly, that's because there was a Linux version for that game (their own wine port). A good way to tell if it's using proton or not for sure is that steamplay message on the top right of the steam library page.
The Steam Play message is missing. But it seems that the downloaded files are for Windows.

The game devs have linux depots and it looks like you need to opt into the linux-version-wine beta branch https://steamdb.info/app/232050/depots/?branch=linux-version-wine.
Closing as this is not a proton issue.
Nothing extracted yet.
The requested runme.sh not exist!