6600 SO2R Headphone Audio Question (L-R, Blended)

Howdy -
I've got my 6600 configured for SO2R and I hear both slices in my headphones. In Audio settings, I have Slice A set to pan fully LEFT and Slice B to pan fully RIGHT.

What I was expecting is that Slice A's audio would be in my left ear and Slice B's audio only in my right ear. What I am hearing is both Slices in "Blended" mode in both ears. What setting am I missing to achieve having Slice A's audio only in my left ear and Slice B in my right ear. Searching for this to no avail.

Using Inrad W1 headphones, plugged directly into the rear of the 6600.