No way. I have had a couple of Rhino-liners and "Line-X" coatings and the material is not rubber, it is polyurethane compound . It is also textured, and i could stand on it barefoot when the steel hood was hot enough to burn your hand. The good spray-ins are no hotter than an Igloo cooler (same material) out in the sun. Besides the best liners come in colors other than black (have for 15 years now, I had a lime-green coating in one truck) and some colors reflect heat better than others. The cheapo DIY kits can come with inferior materials, but I have no experience with the cheap stuff.
I just get incensed when I see people abusing their dogs by leaving them in the bed, while driving or parked. Dogs cool their body temp through thier paws primarily, and standing on hot steel is abuse on a dog, ignorance or worse on the owner. I call 'em in often.