I don’t think you need fancy stuff to reproduce this.
The engine doesn’t care what screen or hardware you have - it’ll output what you set it to output.
Just like you can fuss with DLSS and render 800x600 at 4k you can do the opposite, render 8k down into a 4k screen.
As I said. Widget up a script to go windowed mode at whatever res you wish. So what if you cant see it all? The engine still thinks you can.
Also, it must be some plug in you guys have enabled or something - last time I checked though you get around 19fps 4.27 worked Ok stretched across 3 4k screens.
Ok. Well, 19 fps on a highy optimized scene or just a black screen 
Btw you can try and report a bug - link them this thread. I doubt they care one iota.