The point was made about the legality of Jesus. It is not and never was a point about legality; it was about God's fulfillment of God's promise to us.
The promise to David was that the throne was to be given to one of David's descendants.
Correct; no legalities involved.
You don’t know much about monarchies and how they are passed down, do you?
They don’t elect kings, you know.......
Correct; no legalities involved.
The term used is "seed" (John 7:42, Gr. σπέρμα, spérma; also Ps 89:4, Heb. zera') and seed implies patrilinear inheritance, which is synonymous with legality.
Of course, women were believed to have no "seed". The Jews believed that the woman is a "fertile field" on which man's "seed" (a term synonymous with offspring or descendants) would grow.
This is how the term "barren" or "infertile" originated for women who could not get pregnant. As long as man produced "seed" the "fault" was woman's. So much for bible-based "science" under spiritual guidance.
In Romans 1:3 Paul clearly states that (he believed) Jesus was the product of patrilinear Davidic line:
Inheritance could not be passed on through the mother as the mother did not have the spérma.