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.

Huh, that's pretty neat. I always wondered what that was for.

I wonder if it needs to be dots or if other shapes would do just fine and dots were the cheapest in regard to manufacturing.