The spec [1] doesn't mention how to serialize the individual transforms. This may be fine but still not clear to me for the case:

div { 
  scale: 2;
}
console.log(window.getComputedStyle(div).scale); // serialize as "2" or "2 2"?

If only the X value is given, the Y value defaults to the same value, and If one or two values are given, this specifies a 2d scaling, equivalent to the scale() function (i.e. scale(2, 2) in the above example). However, should we serialize it as "2" or "2 2"? For now, Chrome serializes this as "2 2", but Firefox serializes this as "2", so I think this is an ambiguous part. Maybe the shorter one is preferred?

[1] https://drafts.csswg.org/css-transforms-2/#propdef-rotate