Yes, this appears to be correct - the Firefox API supports filtering out of the box. If you check the readme on the WebSocket companion, it specifically mentions Chromium based browsers, assumedly indicating it's intended for them.
There is also a note on the normal uBlock repo that says that Firefox has an extra feature with a link to inline script tag filtering, which says it does not work on Chromium based brownsers: https://github.com/gorhill/uBlock/wiki/Inline-script-tag-fil...
To be sure there is no confusion, it's possible to block inline scripts with Chromium, but not on a per-inline script tag basis.
Per-inline script tag filtering is possible for Firefox, but the feature relies on "beforescriptexecute", which is planned to be deprecated in Firefox as well[1]. As a result I have ceased to create "script:contains" filters and favor filter solutions which work on all browsers.
Thanks for the confirmation. I expect new engines like Servo to support content and request filtering at a lower layer for efficiency reasons, while of course still exposing it to JavaScript as needed. Opera already does this out of the box, though I don't know the internals and it's not as full featured as uBlock Origin. Without uBlock Origin and uMatrix, the web would be unusable from a UX perspective. thanks gorhill and friends!
There is also a note on the normal uBlock repo that says that Firefox has an extra feature with a link to inline script tag filtering, which says it does not work on Chromium based brownsers: https://github.com/gorhill/uBlock/wiki/Inline-script-tag-fil...