Two claims, kept separate

There is no gas in the metering sense, and there is a native asset. Those are different claims, and conflating them is how fee discussions go wrong.

The first is settled by the architecture. A predicate has a fixed size and bounded verification cost, so execution cost is knowable in advance and nothing needs metering. The live precedent for this property is a predicate-chain design in the published literature whose operations are bounded and whose scripts stay near constant time, requiring no gas [S]. The second is a design premise with architectural force behind it, set out below.