Yes, but often you have elements with taborder > 0.
> It's generally advised not to set tabindex to anything but 0 or -1 and let the document order dictate tab order.
Only if document order is sane. Usually with modern websites it isn't, document order is a broken notion if you can position elements at will and e.g. put navigation at the bottom of a document but move it to the top by CSS. Which is actually a recommendation that some people make for acessibility...
What you usually want to do is assign a sensible taborder > 0 to the one form element that the user is probably currently using. Otherwise, he will pointlessly tab through search, menus, cookie bars and a ton of other pointless stuff first.