SP4 / New Dock / 3 Monitors

[WAR]

I have a Surface Book 2 with the new dock and I am using 2 external Dell Monitors plugged into the dock in addition to the SB2 screen at my desk with no problem.

I am considering moving back to my SB4 and have tried plugging it into the same configuration. In display options, it shows 3 monitors, but the only thing that works is to duplicate both monitors, 2 & 3.

Is it possible to have 3 separate screens with this set up?

Thanks for any clarification!