If you use the bushing technique (which you have described accurately) then you are nearly certain that you won’t rot the plywood around the fastener holes. If you only use sealant there is always the possibility that it could fail and water ingress will rot the plywood.
There was a fellow out near me in Rio Linda, CA who built a very nice Marples/Brown Constant Camber trimaran over a period of many years. After he took off with his wife and cruised for a few years he had to do extensive repairs to the deck because of water getting through the sealant on many of the bolts that held on his deck hardware. This is on a boat that lived in the water, a trailer boat doesn't have as hard a life. But this example does show what can happen if water is allowed to get into the end grain of plywood.