To add to my previous comment- aside from the health aspect, there is the valid concern of food allergies. What if you’re allergic to nuts, but you unknowingly buy some icecream made with the milk of a woman who eats peanuts? What if you’re allergic to shellfish but your donor has been eating shrimp?
There are LOTS of things to take into consideration when consuming the milk from an unknown woman.
Because of the hospital’s goof that caused my breastmilk to dry up too soon with our first daughter, we gave the baby the breastmilk of a friend who was still lactating. We actually asked her about her diet and supplements before taking the milk, though.