Please tell me how swallowing the wife’s milk compares to the breast feeding of an infant. Does not a lady who feeds someone become the mother of that person?

Foster mother in Islam is the name given to a lady who feeds her milk to someone else’s infant with the intention and purpose of sustaining and nourishing the infant. Without this purpose and intention, no one becomes her foster child, if for some reason her milk is swallowed.

This of course is not the case with the husband. So the two are totally different.