Yep as I knew it's a Nvidia drivers issue 100%. Yes laptops only want DP/eDP data to display on the eDP DP_D display, that's it.
X-Vsion told me that some "motherboards" they tested, the drivers don't throw an error 43 and don't set the main display to non-PnP in DP_D mode.
DP_B could display only if there are no drivers + LCD cable disconnected. Yes we need drivers to display more than 1 display thru DP and HDMI out.
The EDID override is handy because it removes the error 43 on the GPU's drivers and allows display in DP_A, C and D. Without EDID override, you can't use the GPU's drivers in windows.