Now, now, now, it's a perfectly reasonable assumption. Who would have thought that an Episcopagan church would have been named after a saint. After all, it's not like there are any Lutheran St Johns, or Methodist St Johns, or Presbyterian St Johns, or Baptist St Johns, or UCC St Johns. Why, of course, when one hears "St. John's," one would, of course, think Catholic.
Well, not necessarily reasonable, but when I was young its what I thought. Catholics are into saints, the reasoning goes, so a church named after a saint is probably Catholic. Childish, perhaps, but no reason to think there was any ill intent. As a young Baptist, there was just us versus all those formal, liturgical places. Hillbilly Baptist, mind you. many transplants from Kentucky and Tennessee. My dad took us there because the Methodists had gone liberal. That was half a century ago. Sigh. Good times. Where I learned to love the Scriptures. Good people.