"Force cleanup on standard paste" mangles text from MS Word unless "Paste from Word" button is enabled

If you check the box "Force cleanup on standard paste" but don't have the "Paste from Word" button enabled on the text format you're using, the cleanup leaves a lot of cruft in the pasted text.

Tags left behind that shouldn't be, on failed cleanup:
Microsoft's if !mso and endif tags
Microsoft's w:whatever tags
Microsoft's o:whatever tags.

Style tags, and all the style declarations within them, are also not cleaned up, though the tag is not allowed in the WYSIWYG filter.

Enabling the "Paste from Word" button, even though there's no need to use it if you've checked the "Force cleanup on standard paste option," makes the standard paste behave as expected.

I can provide screenshots and/or further documentation if needed.