Earlier quoted context omitted.
The current consensus among browser implementors is that, on the whole, prefixed properties have hurt more than they’ve helped. So, WebKit’s new policy is to implement experimental features unprefixed, behind a runtime flag. : https://webkit.org/blog/6131/updating-our-prefixing-policy/ As the article states, prefixes have created a set of problems, which is why Apple, Google, Mozilla and Microsoft stopped using them…
But the things they added aren't behind a runtime flag, but enabled by default and without any prefix, yet not standardized.
I have no idea whether or not there's a WG resolution because the WG is terrible at tracking resolutions.