The fact that John is called the greatest among the born by women means implicitly that Jesus is not born by woman, because otherwise John would be greater than Jesus himself (reductio ad absurdum).
Hence the premise of Gal 4:4 is false for who invented that episode (and there is no reason at all to go against a presumed genuine Gal 4:4).
Gospel evidence that Gal 4:4 ("born by woman") is an interpolation
Gospel evidence that Gal 4:4 ("born by woman") is an interpolation
Nihil enim in speciem fallacius est quam prava religio. -Liv. xxxix. 16.