*Lynx puts on his professor spectacles.
While most of that chart is rather off (my dog never cared about being petted on the feet) there is a reason cats don't want a belly rub. Dogs are pretty much the top of their food chain and they have little instinct for protecting their vital organs, or at least no more than humans. Cats, domestic ones anyway, are both predator and prey. Petting them on the stomach triggers survival reflexes that they need in the wild.
On a side note, this is why small dog breeds are not as good as either cats or real dogs. They are small enough to be prey, but lack a cat's defensive instincts.
*Lynx runs away just ahead of a shower of rotten produce thrown by all the small dog owners.