[css-properties-values-api-1] Is `@property` valid with `initial-value: smaller` and non-unversal `syntax`?

[cdoublev]

The spec wants @property to be invalid when syntax is not * and initial-value is a computationally dependent value.

In current version of Chrome and FF, @property is valid with syntax: "smaller | <length-percentage>" and initial-value: smaller, whereas the computed value of font-size: smaller depends on "the computed font-size of the parent element [...]". Of course, smaller can compute to itself (in lowercase) in other contexts, so they may have intentionally left it valid.

I am not sure why a computationally dependent initial-value should make @property invalid. This is not explained, so I am struggling to determine other cases of computationally dependent values than <length>s.