I wouldn’t rely on the label because efficacy of a product may be marginal but they can put it on there anyway as one of the pests it is effective against. That’s why I keep up with what is working in commercial production. No one in the business uses myclobutanil for anything but blossom blight (earliest stage BR) on peaches anymore.
Yes, the peaches I manage are usually clean, but even when brown rot is in the fruit I’ve been able to arrest it with Indar- MFF should do the same thing, but once every 3 weeks won’t do it for cracked or damaged fruit. You may need to spray it so it is active right up to harvest as I have to do with cracking cherries. That means the week before harvest. The cracks open and the fungicide can’t protect the exposed interior.