When accurate metering is called for we have the tech to do it just fine to far less than <1% error. This is a classic case where regulation is required. Rational capitalist enterprise is not going to fix this on their own. They don't currently have the right incentives.
To 1% volume, like rotary meters, but not 1% mass. At least not at reasonable cost.
But you are right that regulation is the answer, although personally I think direct leak detection is more realistic than measuring gas flows accurately in a system that's already built around low accuracy metering.
Coriolis flow meters in natural gas have been accurate and pretty inexpensive since the 1990s with accuracies better than 99% on the extreme low end and 99.5% on the high end.
Its easy to say that anything is 'too expensive' when the regulatory bar is set so low that it doesn't exist.
Right, you could put a combustible-gas-safe mass flow sensor on every gas line, high and low pressure, at a cost of roughly 100x current rotary and aperture flow meters, but then metering would become by far the largest cost in gas production.