Just to be clear, I'm not a fan boi of DJI. I have always hated the P2VP's pisspoor camera that was fragile and expensive to replace. I went as far as converting the Vision plus to a Gopro. It is still expensive to replace the P3 camera, but I cannot argue on how much bang for buck you get in a p3.
Anyways.. I think we all believe that DJI didn't like working with gopro when in actual fact I think it has always been the other way around. If gopro was friendly, they would have allowed DJI to have full integration with gopro (abilty to control the camera via the zenmuse). They would also have allowed DJI to continue using the patented 30pin Rear Hero Port (Zenmuse H3-2D and H3-3D 1.0). Instead, they forced DJI to redesign the H3-3D 1.1 with the side generic USB port for FPV to avoid being sued. They have even gone to the extent of disabling the Hero Port in the Gopro Hero 4's rear port to work with any Zenmuse H3/H4-3Ds.
So I think gopro burnt bridges and not the other way around. And this probably has forced DJI into and becoming what is now, and hence not opting for a 3rd party option in the P3.