Glass doesn't stick to aluminum. The transom coring (Xl Ply) stops an inch or two before the top of the transom. There is then an aluminum L brace capping the wood and then putty sealing the trim cap over the L brace. It's this L brace that bolts into the stringers and gives Gradys their incredible transom strength. Because of this aluminum brace, they cannot glass the top.
I disagree. They also did that on all models that did NOT have internal aluminum bracing.
The reason they used a cap (aluminum or later plastic) is merely to cover the seam instead of glassing it. The seam is between the hull that includes the transom and the liner that includes the deck and the motorwell. It was common construction technic for outboard models from many manufacturers not just Grady. Most of the seam is covered by the rubrail.
The two pieces, liner and hull, are gelcoated in the mold and look perfect. To join them with glass would require a lot of labor and they would have to spray gelcoat and try to blend it. It would add at least one day to manufacturing, probably two. Thats $$$$$. Thats the reason they covered the seam with a piece of crap aluminum trim. then the marketing department started calling it a "bang plate" to make you think it has some function other than cheaply hiding a seam.