XPS 9320 - Thunderbolt OR USB-C video C output problem

I use my XPS at my home office using a Dell docking station to output to two 4K monitors. Recently I got a portable monitor to have more screen estate when working on the road. It took me a lot of troubleshooting (and replacement of monitors) to realize that my XPS will ONLY output video via USB-C to a USB-C monitor if Thunderbolt is disabled in BIOS.

Of course disabling Thunderbolt, stops my home office set-up from working and I'm forced to constantly boot into BIOS and utilizing the annoyingly short 2 second period you can hammer on F12 to get into BIOS for enabling/disabling.

I contacted Dell chat support and they told me it's designed this way, and there is no other/option setting than doing this BIOS toggling. How can this be? there must be a sensible workaround for this? does this apply to all Dell laptop series or only XPS?  I'll be looking for a new laptop unless I can resolve this.