Hello again.
As with all research, it helps to have some understanding of the "norn's" of the period being researched. And the area that the parties were known to be residing at.
Adoption laws, and adpotion practice in 1905, was not as it is today. Informal within community or extended family was common in 1905.
https://teara.govt.nz/en/adoptionFor a period I was a member of an adoption support group.
LawLink, a legal publication, published info after I drew attention to the fact that a codicil could be required to be attached to a will, to give a child cover under a will, for that grace period [then six months minimum] before the Family Court finally signed off on the full adoption, and the child was legally re-named.
Therefore I'm a little surprised than it is inferred a legally binding adoption was conferred by the Manukau Court in 1905, without apparently, corresponding updating of any civil registered birth.
Though others are more experienced than I,
usually a birth registration number that carries a later year date, in the life of a person indicates a lack of record of any previous registration. It is common to find them dated at the time of first marriage; for insurance reasons; and at time of applying for a pension.
Alan.
Edited in an attempt to be more percise in the point that I wished to make.