Actually, it does not work for me here. testing in Reaper.
I have a 4 channel tracl load the plugin, send audio on all 4 channels, but only get output from 2 channels after the plugin. If I bypass the plugin, I have sound on all channels. The i/o assignments for the plugin in Reaper is left as they are by default (in 1 going to plugin input 1, plugin output 1 going to channel 1 on the track, likewise for i/o 2,3,4).
I also tested letting the plugin generate noise on all 4 channels, like this
a1 rnd31 1,1
a2 rnd31 1,1
a3 rnd31 1,1
a4 rnd31 1,1
outq a1, a2, a3, a4
It still outputs sound only on channel 1 and 2