The question says

mechanical connections and grounding wires are rarely designed for the high amperage

The ground cable goes directly (and only) to the frame, as in this picture

^{Image from Quora}

So all the power requirements take this route, notably the starter motor.

In my experience, it is usually easier and more secure to connect to a frame point than to the battery terminal.

The question says

mechanical connections and grounding wires are rarely designed for the high amperage

The ground cable goes directly (and only) to the frame in this picture

^{Image from Quora}

So all the power requirements take this route, notably the starter motor.

In my experience, it is usually easier and more secure to connect to a frame point than to the battery terminal.