Old wives tale. Freezing will not burst an open container whether it be a prop hub, 5 gallon bucket or a water trough. I keep 25-30 boats year round at the shop and I never drain them and I've never had one freeze and burst in the winter. To freeze and burst it must be a sealed container.

If you have a lot of water INSIDE your lower unit from a leaking seal and that water has separated from the lower unit oil, then you might have a problem.