Comment 6 for bug 1452766

A Web page script may change, add, or remove the page title at any time, during or after page loading.

    document.title = "Here I am changing the title"

So what the title of a bookmark should be doesn't really have anything to do with whether the page is loading. I guess it should be whatever the tab title happens to be at the time. That needs its own mini-spec: what it should be if you're viewing a text file, or an SVG with a <title> element, or a Web page that has a title consisting of only whitespace, or a <title> that's 20,000 characters long, etc.