The benefit you’re describing here is essentially the smaller attack vector in a hardware wallet’s code, as opposed to a much larger computer operating system. Do I have that right?

Exactly.

Hardware Wallets protect you from malware on any Internet connected device you might use - so yes we're in agreement here. I also understand the less complexity = good concept but that is still secondary to the airgap. If you have a true airgap on a clean machine - Bitcoin keys are safe. I'm also advocating here to build a SeedSigner so I have no idea where we disagree my guy!

We disagree in the first two sentences you wrote: "Hardware Wallets do not protect your Bitcoins. The hardware doesn't make your Bitcoins safer." Actually, a hardware wallet DOES make your Bitcoins safer than holding them on your everyday computer. Also, setting up and keeping your coins air gapped on a separate computer is a lot harder, more prone to errors and also more expensive than a hardware wallet. A Trezor goes by 70$. A separate laptop usually not under 200$. And how do you even keep the airgap if you want to send your coins somewhere? As soon as you try to transfer data between your bitcoin computer and your everyday computer (probably with a thumb drive), the airgap is broken. Dedicated malware can also be transferred via thumb drive.