Is this something about American-style gas stoves, or all gas stoves? Why would it be impossible to have a valve with a perfect (or reasonably perfect, obviously nothing mechanical is absolutely perfect) seal? A normal ball valve in a gas line is perfectly sealed; why would the valve in a stove be any different?

What magic world do you think we live in? Everything leaks at all times.

And when discussing policy and things at scale, you factor in the total picture where 80% of the individual examples will be one or more of: damaged, installed wrong, 35 years old, used incorrectly, cheaply designed, cheaply made, etc etc, not the perfect ideal lab example.

To be clear, I am firmly in the 'keep gas stoves' camp because they simply work the best for that job, the alternatives are not actually alternatives, and I don't think any of these articles actually show that they are harmful, or at least stand out from any other source of of stuff in the air.

But of course they leak. That isn't even remotely a remarkable claim. 'off' in the real world only ever means 'mostly off'.