It's an Irish thing :-)
I know lots of examples;
My Dad is Thomas Anthony on his birth certificate and Thomas Joseph on his Baptism certificate.
My Mum was Ann Bernadette on one and Bernadette Ann, she wouldn't answer to either of these as she has always been called Annette.
I have a cousin John Valentine, only ever been known as Val, another cousin Michael Martin, only ever been called Martin.
These are all current day, even my own name is a bit dodgy, it's Helen-Marie Francis but my Mum didn't use a hyphen on my BC so sometimes I use Marie as my middle name, sometimes Francis, and sometimes both depending on my mood. This had NEVER been queried on official documents.
It probably depended on the person filling the official form which name was used, the proper name if they were feeling that way out or, not. If it was somebody who wasn't family, maybe you were staying somewhere when the Census was taken then more likely the name you were known as.
The only time I remember there ever being a problem was when my Mum went to New York, the US customs were confused but, they let her in
