I believe Amel didn't glass the bottom of the bow compartment floor because they couldn't without a door being installed. The floor has a slight contour and fitting a pre glassed piece of plywood into the locker to get the contour right would have been very difficult. I did the bow locker floor/ hawse pipe job a few years ago.
On the rusty chain topic though, one overlooked issue in the chain locker is the bottom grate. On #422 the chain rests atop a non removable grate (a false bottom) and under the grate is the drain fitting leading to the bilge. Only way to clear it is to blow air or water into this fitting from the other side. But that clears it, it doesn't clean it. I made my grate removable by cutting a hole in it when I put in my bow locker door and new floor. I vacuum it periodically from inside the chain locker because it clogs from debris on the chain. Now my chain is never sitting in water inside the chain locker.