actually, it’s (pretty much) the way it should function. “On which pages the ‘Pin it’ button should be shown” option relies solely upon functions given by WordPress core, so e.g. the value of the “Home” setting (if it’s checked or not) is used when WP says that user is trying to access the front page of the website. So when one visits the home page, the ‘Home’ setting is used, when he visits a single page, it’s the “Pages” setting being used, etc. I hope that makes sense.