Why does Roon say I am mixing 7.1 to 2.0

I ue the Procedural EQ Matrix mixer for one enpoint to make it mono as its a mono speaker I stuck a pi in to make a wireless speaker for the bedroom, this works well but I always wondered why it always shows as 7.1 to 2.0 in the Signal path, i removed the extra channels and source is only ever stereo.Does it just work this way by design or is it a bug?