Queens left in the bottom don't die over winter, we have 300 hives that run excluders ( steel) and a friend who runs 1600 hives run QX all year round.
If it gets cold bees will wax them over to keep warm. If there are not enough bees in late Autumn we will take the super off and pack them down to a single for winter.
If you run a few hives and take individual frames to harvest honey then a QX may not be necessary. Without a QX we could not harvest honey by taking the whole super home to extract.
If you take the super off and there are bees on the QX, a puff of smoke and those varmits are through that QX pretty quick, maybe we have smaller bees in Oz.