One of the characters describes being taken to a Catholic Mass as a child. The "first and last" time he was ever in a Catholic church. He describes receiving holy communion under both species. That isn't possible. Non-Catholics are forbidden from receiving communion. His Catholic relatives who took him to Mass would have known that. Also, the chalice was forbidden to lay people until Vatican II (1962 to 1965). Even today, it is rare for Catholics to receive holy communion under both species.