A hardware switch should in theory be more easily verifiable than a software one through physical testing. Running tests on PCB traces to verify that a switch indeed works is probably a whole lot easier in general practice than decapping chips or decompiling and analyzing low level firmware or low level OS components.

But are you going to run those tests on PCB traces on your own hardware? If not, then you have to trust that your hardware is identical to whatever hardware was torn-down and tested. I suppose this is good enough unless your threat model includes someone swapping your computer enroute to you with a modified one.

But even then, are you sure the computer whose PCB you tested hasn't been swapped or modified since then? That Chinese operatives didn't splinter cell it while you were out grocery shopping?