Go to any hardware store and get a piece of tinted plexiglass or acrylic plastic and cut it to fit the opening over the display.Went out to the car and tested it and you are sort of right. If you start with the instrument lights at full bright and start to dim the multi-function display dims as well until the instruments are at about 50% bright at which point the multi-function display stops dimming while the instruments continue on. I like the dash lights at about 25% bright but the display is at 50% so I guess that's my complaint (though I am getting used to it).
I was thinking of cutting a laptop or iPad anti-glare screen down to fit.Go to any hardware store and get a piece of tinted plexiglass or acrylic plastic and cut it to fit the opening over the display.