Not as many people actually KNOW the max recommended zone as know the minimum cold hardiness of a plant, which is why a lot of people leave that blank, but no, that isn't what it means.
Some plants are cold hardy, but would not grow well in very hot places. Hostas, some dogwood trees, some cooler growing stuff that maxes out in zone 8...anything over that would be pushing its limit of heat tolerance.
I am in 9A. I cannot grow hostas, Gunnera, all our dogwoods around here died off when global warming made it too hot (Because where I live was ALREADY the southernmost reach of their range), some bulbs that will grow well in the north do not grow here.
