In the Build 1080 CustomPluginVariables.JSON of Main-Game and Devmode, the Steam Plugin is enabled. Entry is: "SteamPlugin.dll":{ " Enabled":1 }, Is that made intentionally?
Yes. When playing rFactor 2, the plugin does not do anything if you don't have the Steam version. It is there for the dedicated server, which loads its plugins from the same folder. The dedicated server will now always report to both the ISI and Steam matchmakers and it does that using this plugin. If it bothers you, feel free to disable it.