Bug 211356 disabled it because of bug 211351, but the linked CSSWG issue says WebKit behavior is correct.
<rdar://problem/101172926>
Pull request: https://github.com/WebKit/WebKit/pull/5377
Committed 255540@main (44ccd6d3b521): <https://commits.webkit.org/255540@main> Reviewed commits have been landed. Closing PR #5377 and removing active labels.
This "caused" bug 251508.