It's not "can you provide the screen DPI to a window?" people bemoan, it's "can you draw one window across two screens with differing DPIs, transparent to the application?"
I'm struggling to imagine why would anyone ever want to do that. It's not even an edge case at this point, it's over the edge.
I have two monitors, but only one of them is 4k and a couple cm bigger, and I dont like to buy stuff unless I really need. It is good enough for me. But this case also comes up on the edge of my laptop when I have the 4k plugged in at the same time. In the days of eclipse I'd keep the code editor top half on monitor, and the console output on the laptop, worked quite nice.