This was added relatively recently (end of 2022) in https://github.com/WebKit/WebKit/commit/96729fcd8ccfe69a87bf1d779b992f6ecd7a6978 . I couldn't find any hits on Github aside from WebKit forks, so let's try to hide this one.
<rdar://problem/120579213>
Pull request: https://github.com/WebKit/WebKit/pull/22461
Submitted web-platform-tests pull request: https://github.com/web-platform-tests/wpt/pull/43872
Committed 272736@main (f72d16287b1b): <https://commits.webkit.org/272736@main> Reviewed commits have been landed. Closing PR #22461 and removing active labels.