I think it's individual dogs. When I was taking a training course they recommended raisins for treats, then vets said raisins were toxic to dogs. Ditto grapes, and I had a dog who loved grapes.

It's probably similar to people and has a lot to do with gut health and tolerances. My dog Pascal can eat anything, but he has enough drool in his mouth (sign of good health) to dissolve a safety pin (dogs' guts can actually dissolve safety pins).

If you ever come to Maine for a visit, I'll make a vanilla cake and eschew the chocolate!