I think most place people will wear boots as the stems and twigs can be hard on the little toes. Sweat might add a bit of a saline note to some of the wines though.
I have tread on grapes many times in Douro quintas. Sometimes they use a hose to spray off your feet, other times there is a sanitizing solution to step into prior to entering the lagar (granite tank). It is a fantastic experience and I take part in this nearly every single year during harvest. The grapes start out really cold and within an hour the tank is pretty warm. The people hired to do this continue for four consecutive hours with just one break. The longest I’ve had my groups do this is for an hour. It is really hard work, but a lot of fun and even better when there is an accordian player and other Portuguese doing the stomping, after the initial work, the “Liberdade” is played and people are dancing to the music on the grapes. You’ll never forget your first time, that’s for sure!