Description
For the transform property, the spec says that
Computed value: as specified, but with lengths made absolute
Value: none |<transform-list>
<transform-list>=<transform-function>+
and provides a procedure for serializing transform individual transform functions. This seems to imply that the computed value should be serialized as a list of functions. Furthermore, there are procedures such as interpolation which expect computed values to be lists of functions.
Later in the spec there is a section
Serialization of the computed value of
<transform-list>
which gives a procedure specifying conversion to a matrix, an operation which does not round-trip (round-tripping is necessary for css transitions) and relies on the box size (not allowed for computed values). Although this makes sense for serializing the resolved value (which is returned by getComputedStyle()) specifying this happens to the computed value looks like a confusing typo to me.
This may be a historical oversight from before the difference between computed and resolved value (sometimes historically referred to as computed value serialization) was fully clarified. We should correct this.