It seems to me Brigham Young was stipulating that the manner/methods of human procreation are necessarily binding on how God procreates. I don't see any rational basis for this supposition. There is no equivalence between God and man. God cannot be "reduced" to human criteria. (Nor, it seems to me, can man be "elevated" to divine status.)
God is Life. God is Spirit. He is subject to no law; for He Is Law — i.e., Truth (Logos).
To be preoccupied with the "hows" (on the crudest basis) of the divine Incarnation is to miss the point that this Incarnation is uniquely, utterly, absolutely, everlastingly Divine.
But once you realize that, then you understand God could have done it any way it pleased Him. The Holy Bible testifies that He did it in a particular way — via the Holy Spirit. And moreover, that the virginity of Mary was in no way inpaired/compromised by this particular way.
And at that point, I for one recognize that human speculations in this regard are altogether pointless, futile.
Not to mention divisive.
But my own spirit rings to the Truth of what the Holy Scriptures say in this matter.
I agree. In light of your comment, "there is no equivalence between God and man," Mormon contextual beliefs in this regard are:
(1) God was once a man (hence, Lds already reduce the heavens to mere anthropology);
(2) They "upgrade" mankind to the status of eternal spirits (as in eternity past -- who are "gods-in-embryo" -- and hence some will grow up into full-blown gods!)
They do precisely what Lucifer did -- yank God down -- and seek to ascend their own divine throne. (See Isaiah 14:12-14)