Breastfeeding went out of fashion after WWII and didn’t catch on again till the 70s. She would have been in the minority if she fed the kid the way God intended.
http://www.popline.org/docs/0334/790055.html
Karen Pryor’s book “Breastfeeding Your Baby” was published in 1963 and became the “bible” for mothers wanting to get back to the natural way of feeding. It took a decade or so to really catch on.
Barry 0 most likely was fed from a bottle.
I read your link and it quoted findings from one (1) doctor.
The Le Leche League formed in 1956 and had one year in 1957 where it declined, but resurged in the 1960’s and 1970’s
http://www.faqs.org/nutrition/Ar-Bu/Breastfeeding.html