Lethal doses of Xylitol for dogs is 0.5g per kg of pet weight, while for chocolate it 5g per kg for pure baking chocolate all the way to not being lethal at all for white chocolate. We're talking a magnitude of difference is lethal even for the most potent form of chocolate, and for dark chocolate it's 15g/kg versus 0.5g/kg for xylitol.

To give an example, a typical hershey's milk chocolate bar is nearly impossible to kill your dog with, even if it's a small dog.

Most sweets are not 100% sugar or xylitol either. You‘d need to compare cocoa powder to xylitol instead, not the diluted form (baking chocolate).

How much xylitol is there in things that a dog might eat? When I imagine any kind of artificial sweetener, I assume it's hundreds or thousands of times sweeter than sugar and the quantities present are correspondingly lower.

Xylitol is roughly as sweet as sugar, unlike others.