that topic is about the hide details feature, not oneboxed local links.
i’m not sure it’s really possible to do what you are wanting. there is no setting and i am certain any component will require a rebake of any existing posts. i tried a bit of a hack at this with an initializer but it loses the formatting and kind of breaks the oneboxed text from the link. and it required me to adjust the Post onebox maxlength site setting to something really high like 100000.