One thing I've learned about RVs is there is no standard mattress sizing. My first camper had a king label, and if we slept sideways, stacked front to rear, it'd fit three people. As I need frequent pee breaks I slept on the outside; my bride had to crawl over me to get in/out. The third position didn't get mattress access (poor Sassy, my boxer). Besides its' orientation it was comfortable.
My second unit was labeled a Queen; I suspect it was designed for very little people; side to side it was - at best - snug, however front to rear it was too short for both of us (5'6"). For one person, sleeping diagonally, it was comfortable.
Learning from those two experiences it became one of our shopping points with our next unit. We're now both quite happy with our Bighorn mattress (a modified king), both in comfort and actual size.