The words man and woman denote a human male and female respectively, the same as the words stallion and mare denote a horse male and female. An individual producing sperms is a male and those producing eggs is female. Therefore if they try to include some people who produce eggs into the man category they include them also in the male category. There is no difference between meanings of of the words man and human male, they are synonyms. You can't say that a man is not a male. Just opposite, if you say somebody is a a human and a male you say he is a man. There are no men producing eggs and no women producing sperms.