Yes, it has been like this since the beginning. See https://www.xwiki.org/xwiki/bin/view/Documentation/UserGuide/Features/PageEditing#HTitleBehavior . In short:
- page name is used in the page reference (technical, used in code) and page URL
- page title is used whenever we display / list the page in the UI
Yes, because the navigation tree displays the title. We only display the page title in the UI, not it’s name. But sure, the page name can be the same as the page title, but it’s no necessarily the case.