OK, I did a bit of research, and of course you guys are right. I still think it doesn't make much sense, but at least now I know why: it's government regulations that mandate the rating!
FWIW, every tire I've owned has simply stated "Max. load of xx at max. pressure of xx." IMO, all manufacturers should do like that of Venger10's tires and explicitly state that the max. pressure is "cold".