I'm in the same boat here, copied the ddl to the bin64 folder, SC does know when RF2 starts or ends but it's seems it is not listening to the game.
If i don't manually add RF2 under the configuration tab on SC, it doesen't find it on it's own.
I added RF2 manually , set the steam.exe as game exe and manually added -applaunch 365960 -silent and wait for rfactor2.exe , tried to tick and untick "watch for this game bla bla"..
After doing that , SCis able to find RF2 as a new game to add the button at the home screen.
Opening Steam, then SteamVR, then SC, then Rfactor2 (either from steam or simmcomander) and SC sees when the game is started but shows a "!" mark in the plugin check instead of the normal check sign.