This matches the name in the CSS Typed OM spec. https://drafts.css-houdini.org/css-typed-om-1/#cssstylevalue No behaviour changes.
As the parser was trying to directly unwrap an unresolved duration. Currently we are outputting the wrong results for the serialized duration, but this is still a step forwards. Fixes a crash seen on: https://evaparish.com/blog/how-i-edit