Reporting back again - nice lady at the Prefecture had told my partner that she got mixed up because there were two people with the same name. We thought she must have meant same surname but even that was fairly surprising as it’s not that common a name…
Anyway - just found that there is someone with an identical name - forename and surname, living less than 40km away from us. There are only 19 people in the whole of France in Pages Blanches with that surname. Just shows - shouldn’t make assumptions!