According to https://github.com/w3c/csswg-drafts/issues/8996 It's ambiguous in some cases, especially when followed by length.
<rdar://problem/111750372>
Pull request: https://github.com/WebKit/WebKit/pull/18043
Submitted web-platform-tests pull request: https://github.com/web-platform-tests/wpt/pull/42112
Committed 268291@main (860ac0eb3e14): <https://commits.webkit.org/268291@main> Reviewed commits have been landed. Closing PR #18043 and removing active labels.