I'm not aware the type of account linking have anything to do with the mod, but the mod does work in co-op.
I use a mod account (on emulator) to carry my main on co-op, so far so good.
Restart the app if you need to.
However i do not recommend you host members of the public with this mod. You risk other players reporting you if they feel something is wrong. There is no report button, but it doesn't mean they cannot send the devs an email with your account name for investigations.