Indeed, the ellipsis means some kind of dialog box will open. Regarding the wording "the user must provide more information", that's what that dialog box is for

Indeed, the ellipsis means some kind of dialog box will open. Regarding the wording "the user must provide more information", that's what that dialog box is for, while also providing a "cancel" option so that as you say, the user can back out. Surely "Attach Files..." brings up a file requestor, so it's exactly the correct use. I can't see why the blogger thinks otherwise. It's just a small nitpick though. The article generally seems to do a good job of highlighting some frankly shocking (and worrying amateurish) problems in these menus.