As Ana Tudor discovered, the CSS prefix helper libraries used by CodePen don't fix
Edge supports both versions. WebKit and Blink only support the
-webkit- version. Firefox supports both versions, but only as a single value, not part of a background stack.
In short: for compatibility, you still need to use
(And in production, either use an
@supports test, or use
-webkit-text-fill to make the text transparent, so it only turns transparent in browsers that support the extended
-webkit- text options.)