OK, Apples to Apples then. Slides add weight, so it's possible Nexus used the 208 WB because of the big slide forward of the rear axle.
But Axle also means Wheel Wells, and I firmly believe styling takes precedence over engineering in some cases. The floor plan has to have places to hide those raised areas that break up the flat floor. So they hide the wheel wells under kitchen appliances, like our fridge, or the bathroom, like our shower pan. Pretty sure that's why there's a domed skylight over the shower, gives some headroom back.
So... Wheelbase affects weight distribution and weight distribution affects handling on the open road. You don't want to be rear heavy/front light. I doubt a 31-foot coach with 208 or more inches WB is going to have that problem. Many builders are now weighing each unit prior to shipment and including that on a sticker. I really wish they'd show Front and Rear, all Four Corners even better. Then you know weight distribution is right.
I've suggested that a test drive include a Travel Center (21st century political speak for Truck Stop) where you weigh the coach and then adjust tire pressure in all six according to axle weights using a tire manufacturer chart. It could easily change how the coach drives, and might bear on a purchase decision.