To clarify, I was responding to the claim that

Several trans females have been able to breastfeed so we are talking about real breasts.

Lactating, or having the potential to lactate, is not the same as being "able to breastfeed." I define "being able to breastfeed" as it pertains to humans to mean being able to provide a human infant with milk from the breast that provides all the exact nutrients and immune benefits needed to keep an infant alive and is tailor-made and optimized to support the child's development. As an infant child develops, his or her nutritional needs change as well - and through a complex process not yet understood, a woman's breastmilk changes to meet the child's needs.

Also, I know that the Scientific American article cites several stories of males who supposedly breastfed their children. These anecdotal reports come mostly (entirely?) from Western men who were visiting "exotic" countries/locales for the purpose of coming up with anthropologically-oriented, Ripley's Believe-It-Not type stories of the unusual, amazing things things that "primitive" people in strange "foreign" lands do so they could sell them to the press. Collecting and spreading such stories used to be a stock-in-trade for traveling men from the West.

None of these stories was actually proven to be true, and I suspect they are apocryphal. I also suspect that the men who told & sold these stories actually had very little understanding of the biology of breastfeeding.

Yes, some males lactate coz they have a pituitary disorder or disease. Some males in extremity such as Nazi death camps were said to have spontaneously lactated due to the high stress. Sure, a hungry baby on a man's bare chest will try to suckle, and a man certainly can provide an infant with emotional comfort and calm through such contact - and if secretions are coming out of the man's nipples, a baby in such a situation might ingest them. But none of this is the same as being able to breastfeed an infant/child.

New mothers customarily lactate - but for one reason or another, many lactating women have found they could not breastfeed. Lactating and breastfeeding are two different things.