Ah, I thought you were displaying on both outputs, not switching between them, hence my mirroring comment. I suspect XFCE, not the DM, detects the output change and takes care of it. You might need to emulate that behavior with a hook of some type that you have to setup yourself with the tiling WM, and you might have to --off the unused display. I’d be willing to bet you can find some sort of hook script out there that can do this, I seem to recall an autorandr program I used in the past where you could set up output profiles. I hope that helps, maybe a little bit.