Agreed. I have a retina mbp that I use as the 3rd screen plugged into a 4K monitor over usbc and a 1920x1200 over dp. Everything works fine. Windows stay in the right place when plugging/unplugging, etc... My eyes also thank me every time I look at the 4K text on my main monitor. I’m debating buying another one and dumping the 1920 monitor.