An air gap is a product decision, not a decoration.
The useful part of being offline is not the theatre. It is the boring, repeatable fact that every transaction crosses a visible human checkpoint.
Better Wallet Pi treats the camera and screen as the complete communication surface. The online machine may render a request as light. The offline device may answer with light. Everything else is excluded from the core flow.
That choice changes the product. There is no background sync to trust, no driver quietly asking for access, and no cable that becomes a second protocol surface. The user experience is narrower, but the boundary is easier to reason about.
The tradeoff is deliberate. An offline signer should be slower than a browser extension. It should ask you to look, compare, and approve by hand. That friction is part of the security model.