All internal combustion engine exhaust, run in the 600 degree + range even hotter under load . Proper heat shielding to combustibles and testing of same is what the manufacturer should be doing.
I know that after 8 hrs on the road , the bed in my coach has heated through very nicely for the cool fall and spring evenings that are common when I'm traveling.
Maybe not so great if I travelled mid summer.
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.