I have only one pressed DVD and it is a dual layer.
My 1693 and 165h6 can read it fine, and CDspeed shows it to be a good disc.
But my 16a7 has a very difficult time reading the second layer. CDspeed Disc Quality shows the first layer to be good but the second layer has a huge amount of errors. The transfer rate test aborts at the layer break.
So in my experience, the six series is the last series that can handle a dual layer pressed disc. But I don't have the new 1 series.