someone has complicated this far beyond what is intended. When it tells you following seas, it means currents. And if you have a fair wind and your jib has a full draw, you don't need to worry excessively about being pooped.
the saying is one another "sailor" would understand. Sometimes years at sea on a masted ship this was a way to wish another all the most favorable conditions for speedy travel to their destination. in the case of a death of course this is wishing them a speedy trip to their final destination.