Jim, I had not noticed that similarity, but you're right! I also notice tune similarities, usually in the chord progressions and melodic intervals. I've learned on Mudcat that this is very subjective, and not everyone hears the same thing.

In this thread about the hymn tune Resignation, I hear so much similarity with the tune St. Columba that I get the two mixed up. I also happen to like both of them and created this short page to show the similarities. ;-)