Greetings humans
This behaviour looks (and sounds) correct to me.
Voices are summed and pumped into an fx buss.
With distortion on buss 1 the waveform is changed.
With no effect on buss 2 the wave form remains unchanged.
When both activated together fx buss 1 and 2 outputs are mixed and the resulting wave form is a blend of the 2.
Check it out on your scopes, dist buss1 then no dist buss 2 then both buss together.
This is the same result as the mixer module on HW synths where you can blend 2 or more waveforms to get that particular sound
That does not occur from any of the component waveforms.
I think this result is similar to the ultra saw effect, mixing phase shifted copy of saw back with original saw for that xt ra bit of edge.
Peace luv and aciiid