That must have been seaman’s twist of the story.
I don’t know much else about this sect then that they indeed believe the Mahdi shall be born from a man. It is an other version of the virgin birth but now with a man as intermediate.
I never undertook a serious research on this - only sporadically came in contact with the subject - so I can be mistaken, but my impression is that this must be a locally surviving offshoot of Alavism influenced by pre-Islamic Iranian beliefs, Christianity and Zoroastrian influences. I can ask a Turkish/ Kurdish connection of mine if he knows more about this, but this I can not do now.
Yes, that is true.
Needless to say that such stories/beliefs have as little to do with the core beliefs of Islam as believing that rain is dry.
About the concept of the Mahdi there is no discussion in Twelver Shia Islam. The twelfth Imam disappeared as a child and since then lives hidden until the time is right to come forward again.
You can encounter Sunni Muslims who under the influence of Shi’ism, popular belief/stories, cultural influence, interpretation/mixing of the stories in the Hadith have cultivated a belief about a Messianic Mahdi figure.
Salaam.A