The point is - you can verify it yourself. Without trusting anybody else.

Dumping the firmware means you can ensure it's not been modified (presumably from when you uploaded it to the device yourself).

Being able to inspect components means you can ensure it's still exactly as you built it. And if you haven't, you can visually check that it does what it says it does.

If you're not technically competent to make this verification, you can ask somebody you trust and who is to do it for you.