That's a long propagated falsehood. A mistranslation of "Amazon" to " one breasted" vs more correct translation ( warrior)
https://en.m.wiktionary.org/wiki/Amazon
This was fed by the Greeks' villainizing ,"the other".
Obviously the Amazons would have to be more like men if they were such able warriors. And clearly they would hate themselves as women do much as to mutilate themselves.
There's no ancient depiction of the Amazons that shows them as so mutilated. And it doesn't do anything to improve one's ability to use a bow.