The human medications are labeled as such because taking the medication orally will not help a vaginal yeast infection. And frankly, a lot of people are stupid. That's why there are warning labels on everything. You need to get the antifungal where the yeast is. In this case in the crop.
All of those "zole" family of medications are nearly the same antifungal. Many people have successfully used the OTC versions especially when vet care for a chicken is not an option. Vet prescribed meds may be more pure but this works too. It does not harm the chickens as there is nothing toxic to the chickens in the cream.