This is one of the reasons that the following WPTs are failing: css/css-ui/compute-kind-widget-fallback-props-revert-001.html css/css-ui/compute-kind-widget-no-fallback-props-001.html
<rdar://problem/98407667>
Our behavior does match the current spec, so the tests have actually been fixed by https://github.com/web-platform-tests/wpt/pull/35412. This might still be a good enhancement to consider.
STP170 passing this test: https://wpt.fyi/results/css/css-ui/compute-kind-widget-fallback-props-revert-001.html?label=experimental&label=master&aligned https://wpt.fyi/results/css/css-ui/compute-kind-widget-no-fallback-props-001.html?label=experimental&label=master&aligned Marking this as "RESOLVED CONFIGURATION CHANGED".