I'm not really disagreeing with any of the good comments here. But I'm thinking there appears to be some flexibility with Sonar's steps where some of the others in a one step merge don't tell exactly how they're merging?
If they all are automatically panning hard L-R then merging that would be good. Or does the User still have to pan hard, then save as a mono then select both to merge?
I've merged / stereo in Sonar quite a bit and it seems to work well. Of course less clicks are better, I'm not saying that's not. Convenience it's always good!
But IMHO I've not really thought this as too much an issue.