Seems like it might be similar for ⧼whatlinkshere-whatlinkshere-target⧽ & ⧼whatlinkshere-whatlinkshere-ns⧽ as well.

edit: removing the :nth-child(3) from the JS snippet in the task description finds these additional elements for me:

$( '#mw-content-text > div.mw-htmlform-ooui-wrapper.oo-ui-layout.oo-ui-panelLayout.oo-ui-panelLayout-padded.oo-ui-panelLayout-framed > form > fieldset > div > div > div > fieldset > legend > span.oo-ui-labelElement-label' )

These messages are not supposed to exist or be shown. They're used in the HTML, because the form uses HTMLForm sections in order to target some field groups with CSS and display several fields side-by-side instead of on separate lines. Using form sections causes these headings to be added, and there doesn't seem to be a way to prevent that, so they were hidden with CSS as well.

This could perhaps be implemented better (or maybe it could use a less customized form), but the behavior is intended.

There is something similar on Special:Contributions too, with the messages ⧼contribs-top⧽ and ⧼contribs-date⧽.