Maybe it is not the fact that they cannot pass gas, all I know is that it kills rats and mice, somehow.

I did not believe it either. I was in a guys shop about 5 years ago, and noticed several dead rodents and these containers on the floor with a liquid in them. I asked and he told me how he kills them, and explained how it kills them.
He may have been wrong on how it kills them. He changes the coke every few days, after the fizz goes away.
Maybe they die from a coke habit/overdose.

Things must be slow for lawyers right now, you did a lot of research on the gas subject. Interesting.

I have been using it for the last 5 years, and I have no mice in my work shop.