The digestif isnt the wine you drink at dinner though, it's the (different) wine you drink after dinner, and it really is very different. For example: small prosecco before dinner, then red or white wine with the food, and then a Fernet Branca at the end of the meal.

Digestifs seem to often have a bitter or aniseed element in them. I wonder if that is now known to have a legitimate scientific basis, or if it's just some kind of Mediterranean historical accident.