Yes, exactly. You can think of the 4 mono channels as 2 stereo processing tools, each one in order to get a control on ‘real’ stereo panning and / or stereo balance.
Ex: Morphagene left out > A-138s in1 / Morphagene right out > A-138s in2
Or: Monsoon left out > A-138s in1 / Monsoon right out > A-138s in2
Because you need the stereo image of a sample in Morphagene or that of the reverb from Monsoon to be better positioned in the song, or it can also be too wide. So, apart from controlling the stereo image for artistic purposes, you can use it to get a good (or better) phase correlation. The more you reduce the gap (in other words, the more you tend towards mono), the less you get problems of phase cancellation, especially with the bass spectrum.
(This phenomenon does not occur in headphones because the left-right sound distribution is necessarily separated, but it can dramatically happen in the case of monitor diffusion. The vibrations of the left and right loudspeakers cancelling each other out... and parts of the song sag or disappear!)
'On ne devrait jamais quitter Montauban' (Fernand Naudin).