It's a style guide, just like any other. Honestly, unless someone points out an error, the error isn't there. If people read over the "error" without stopping, it isn't much of an error. People are going to understand the possessive meaning of Jules' and Jules's, either way. I like the Strunk and White guide myself. I think it is a safe, non superflouse way of writing. I can't claim to adhere to it one hundred percent. But I think it is a good place to start. But people can pull from many grammatical sources to justify corrections that they deem important. Most grammar text books are harder to follow than Strunk and White's guide. I highly recommend it.