I thought the transition from pure black to window with dots was made for thermic reasons, so there is not a hard line between hot and cold glass, and with that less stress on the material.
The complete black border is probably for holding it to the glue, I suspect.
the windshield glass in modern cars is bonded to its frame using a strong and long-lasting urethane adhesive.
"This makes the windshield a structural component of the vehicle's body," explained Reina. "The frit is black painted enamel that's baked onto the surface of the glass, and it provides a secure point of contact between the glass, urethane adhesive, and windshield frame."