I think one of the main points of the encyclopedia article as well as the Pagan source I linked and quoted from on my last post was that the Persian version and the Roman version of Mithras are not connected in any meaningful way. The two would have to be shown to be from the same religion/mythology for the anti-Christian claims to have any meaning. So it doesn't really matter if the Persian version had a virgin birth; it wouldn't support the Jesus-is-Mithras claims, anyway.
Oh, sure. I was kind of saying the same thing in my own long-winded way upthread somewhere. I suppose if one really wanted they could argue that the Christian story and Roman Mithraism share a common ancestor in Zoroastrianism without directly influencing one another but, aside from that suggesting that the water goddess birth account was more prominent than it appears to really have been, that would suggest that in this sea of gods and goddesses and births and creations coming about by all manners imaginable, any two vaguely similar stories across times and places (in this case, impregnation without sex) are themselves like parent and child to one another.
(My personal favorite story that is often claimed to be connected to the Christian account of Jesus is the "resurrection" of Osiris.)
What I find a bit ironic is that these fake Mithras and Osiris connections are also used by some fundamentalist groups to show that Catholisism is actually pagan.