dude no they dont specify, you get a Xbox console, its all good though, if the box does die just swop it out for a newer one. Im guessing if it lives past the warranty it will keep going for quite a bit anyway
The RROD stuff seems to happen pretty early.... so ja just keep your receipt and if in 3 years it does decide to go tits up swop it in, the core models have been discontinued so the chances of you getting a swapped out core are slim.
I used to have a core model i bought from launch, one tip was to keep the power brick suspended in air, give it maximum exposure to air, i sold that box to a dude, he says its still going strong, and they TORTURE the thing just like i did, the box has been going for well over 3 years now, still going strong