I don't use the method that adds it to the Home Screen because every time you use it it opens a new window in Safari. I don't always close out of windows, but I have been checking this site when I have a few minutes at a time. If I did it that way I'd have twenty pages open before remembering to close them all.
Huh. They must have changed it, then. I tried the Adding to Home Screen trick a few years ago which is when I kept getting multiple windows. I haven't tried it since then. So, ignore my statement above! :-)