If I am not mistaken, CSSCounterStyleRule.name should ignore symbolic counter styles, because they are invalid.

The keywords decimal, disc, square, circle, disclosure-open, and disclosure-closed are valid <counter-style-name>s, but are invalid when used here to name a counter style rule; doing so makes the rule invalid (related issue: #3584).

https://drafts.csswg.org/css-counter-styles-3/#the-counter-style-rule

-  If the value is not "decimal", "disc", or "none", replace the associated rule’s name with an identifier equal to the value.
+  If the value is not "decimal", "disc", "square", "circle", "disclosure-open", "disclosure-closed", or "none", replace the associated rule’s name with an identifier equal to the value.