From reading the Steinberg PDF from the last update, it seems Steinberg wants us to apply a mono output to render parts. But then after you render it, it’s going to only sound through one side so you would have to either put it back to stereo or perhaps drag it to a new track, then you would have to rename that track.
I for one would prefer to have a mono option in the render setup window. We expect it to be there, it would be less hassle and more intuitive to be there.