True to some extent, certainly. But if a cop in Arkansas catches you stealing a catalytic converter, the rest of your day is going to play out very differently compared to how things would have gone in SF.
I don't doubt it. I doubt the cops' unsupported claim that said difference is an effective deterrent against the crime.
We'd need some solid numbers on converter theft rates relative to the car-owning population. But even then the numbers wouldn't be comparable, so it'll always come down to my "common sense" versus yours. My common sense says that when cops see a crime in progress and walk away whistling, it encourages further crime... and also discourages the victim from bothering to report it.