The breakout board allows connecting PLT to DUT without a PPC: instead of pogo-pins, wires can be connected directly between breakout board and a pre-production sample. This can be used to make sure the test plan works with the DUT. With the breakout board, if you discover, for example that you need to connect a test point to RDTP01 instead of DDTP00, you can simply change the wire. Once everything is working, you can ask us to make a PPC with the same wire connections that you ended up using with the breakout board.
You know best how your device is supposed to behave
Start developing the test plan before finalizing the design of the PPC, and before the PPC is ready.