Write the test on mocks. Prove it on the bench.
Waiting for hardware usually means waiting to write the system test. With mocks, the test is written, run, and passing before the boards arrive, and when the bench is ready, the same plan runs there.
That changes what the first day on the bench is for. Instead of fixing payloads and working out the order of operations against a device that is also new, the team arrives with a test it already trusts, and spends the bench time on the question only the hardware can answer.