I wonder if you have seen this before. In my tree I have a couple that married using the maiden name of the groom’s mother on the certificate. The marriage was at the “parsonage” in the Victorian goldfields in 1882.
A year later the couple had a child and just reverted to using the husbands “proper” name and continued to do so.
It turns out the couple had a child two years before the marriage. There was no birth registration for this child, and I only know about this as the child was noted as “issue” on a birth certificate some ten years later. I guess the earlier child is connected with this, but it’s still not clear to me what this subterfuge was meant to achieve?