If it's a mono signal distributed across the KPA's stereo outs, the two halves will be phase-coherent.
If you sum them in a DAW, there'll be an increase in level, but that's about it, so in such cases one might as well record only one of the stereo-out halves (L or R).
This is true. But if you have any type of stereo effect on, like rev or mod, it would be a different story.