Son and Daughter refer to a sex binary, so non-binary non-physical stuff doesn't come in to play here.
Male/female is determined by chromosomes, either XX or XY.
Seriously however, any link to where this is specified in the way you claim it to be? How does it see SRY gene disorders? If your child is a daughter to you but technically has XY, will the law mandate you to declare her as a son? etc.
This isn’t true legally (where “sex” is really an ascribed gender assigned at birth and possibly updated later for a variety of reasons) or medically (since an individual with a 46,XX karyotype can be male or female medically, as can an individual with a 46,XY karyotype.)