My husband says it is not a Roman Catholic practice to choose a saint as one's special patron at confirmation. I was an adult confirmandi and was asked if I wanted to do this, and I chose St. Maria. I need to convince my husband, who was born a Catholic and confirmed in Italy. He says he never heard of such a custom.
It’s a custom, and not a universal custom at that (as is demonstrated by the fact that your Italian husband never heard of it). The reason it was done was to encourage young people to better appreciate the communion of saints and to develop their love for the saints. These days, in many places local dioceses encourage confirmandi to continue to use their baptismal name – which should be a Christian name – in order to better link the initiation sacraments of baptism and confirmation. In these areas, only a confirmation candidate who had not been given a Christian name at birth by his parents would choose a Christian name for confirmation.