I certainly would not want the top of my mast
taking significant bending loads in an effort to stop the boat rolling. This sounds like a bad idea.
We have a lot of natural surge and rolling where I keep the boat. 1/2 inch nylon docklines last 3 months. I added snubbers and they now last almost a year.
Trying to stop the boat from moving is a fool's errand in my opinion. The jerking and snapping put tremendous stress on the boat cleat. We unseated two cleats
before I got the snubber clue.
Our best success over time is with the boat tied off "loosely" in the middle of the slip with snubbed dock line lengths adjusted so the boat can't hit any part of the dock and then let it move around. With double slips and no center post this is really hard to achieve.
In a storm I can see the need to cinch it up tighter but I certainly would not consider securing it to the top of the mast.