The dust cover/bridge on a FAL has to be really screwed down to give a good scope mount. That’s another “plus” for Stoner’s original AR concept. The flat top doesn’t need an aftermarket bridge added and bolted on.
Don’t get me wrong, I think FALs are fantastic.
The flat top is a new design. The original AR design had an integral carry handle. Early optics like the AN/PVS-2 had custom mounts that mounted beside the handle because they were so huge, but for practical purposes the only way to put modern optics on an early AR is to replace the upper.
A quality FN dust cover makes the rifle stronger. A touch of Loc-Tite in on the screw threads and it might as well be part of the rifle.
I have a simple dust cover that only accommodates optics but some of the more advanced ones will allow loading of ammo from stripper clips and the attachment of a brass catcher. Very versatile.