I'm wondering if someone else's BM is as good as your own? When there is illness in a house, the germs are passed to the mother via nursing, who creates antibodies and gives them to the infant via BF. If that cycle doesn't exist (which it doesn't using donor BM) it can't be as perfect as a mother BF her own child in their own home, KWIM? Likely the infant is getting antibodies to illnesses they aren't exposed to at that time. They also aren't bonding with their mother in the same way.

All that aside, I still support it, even if I wouldn't do it that way myself.