This category isn't just for Jews who converted to Christianity...any and all religions are included, including those Jews that 'converted' to non-religion. However, if you want, you could help by adding this category to all of the former articles that you added Category:Jewish converts to Christianity to. In the interest of representing all faiths, Wikipedia MUST have a category for former Jews in the Category:People by former religion category or else they all need to be scrapped.