Wondering if OP has done the screwdriver test yet...
Thought about it again, maybe the joint is more like this picture which could explain a 'layered' look to the exposed material between the fiber-glassed areas.
I read somewhere that some Bene's have the deck
joint with a polyurethane adhesive
, this transom to hull
could be similar.
Again, I would ask some actual Bene owners directly in case our collective conjecture is not 100% correct.