I'm sure that Ambarella A9 is the P3P chip (full features). The Ambarella firmware code is slightly different between P3A and P3P, but same Arm Cortex-A9 code. Second, A9 chip (P3P) has VHDL (for FPGA hardware part of the chip) compiled code section encripted, that P3A chip doesn't need. For what I guess (after long time experience in embedded system programming), it is that the Ambarella made a specific A9 masked chip for DJI P3A and due to numbers involved this has offered at less cost, making possible the same hardware PCB design.
But if someone has the good will to tear down both cameras ....