I believe the "one"/W371 stack is always a single full range channel.W371 do also work as stands for the Ones.
I wonder what kind of wiring/connections would be made if Ones+W371 is used in a multi channel 5/7.x.y setup. Will x be 2 or 1 or 0? Normally receivers have dedicated sub out, but W371 recommended wiring is inline-path of Ones.