I've heard that a number of times over the years. It makes sense because looking at your sewer connection while eating is probably not the best dining atmosphere.
Yet, others do offer floorplans with opposite side dinettes but they just don't seem to sell as well. I think that part of the problem is that DS slideouts are deep and have a flat floor drop-down so they are best placed away from the patio area while PS slideouts are not as deep and the slideout mechanism doesn't intrude on the basement hatch space as much so they work better on the patio area. It would be nice though if they could work it out to have the best of both worlds.
To me, the best thing that would come out would be a 6 slide coach. The front and rear caps would extend out about 6' each. That would give you a shorter more maneuverable coach but yet could extend out to about 50; of living space. Hey, as long as I'm dreaming - might as well dream big.