Catch, I read it, I dissagree.
If the components are aligned vertically above each other and the sea cock is open and the valve at the hose is open, mother nature will do her thing. Can't fool with mother nature, ultra dependable.
As far as hoses go, especially elastomeric ones, if both ends are free bore by opening valves to the atmosphere or an emply space, whatever water is left in the belly of a hose run will push out both ways to make up the added volume while the fluid is being transformed to a solid, long before it can stop and expand enough to do anything to the hose, at least in the climates we live in.
Gravity draining the system as I described creates massive voids for any residual left not to to reap havoc. Can't leave that sea cock closed though.
Of course there's nothing wrong with doing more as a precaution or to keep the marina guys working, I do it all the time. I see advertised a kit for winterizing outboard motors too, even shows the setup with the hose and tank on the outboard motor of a trailered boat - I'm sure they do well in sales, me I'll pass.