Perhaps one of the writers follows this group because there have now been to hints that George is not Jewish.
1. He was delivering Christmas presents to his Parents (not for, he just happened to run into the neighbors while he was at their house)
2. In the Rye - George says " Oh mother of God", obviously this is not a phrase that a Jewish person would use.
An aside, when I saw what the episode would be about in the paper, I could just imagine George's Folks with Susan's Folks - suprised no one thought of mentioning that angle here before eg: the inlaws. Naturally the Castanzas, as always, had me roaring, they have to be the best recurring characters on the show.