AFAICT that’s correct for WebBluetooth indeed, as it’s only implemented by Chromium (and thus all browsers relying on it) but for but for WebUSB https://wicg.github.io/webusb/ it’s still being discussed at the W3C level so even though not standards (which I don’t think W3C even produce, only API specifications, e.g HTML isn’t a standard whereas Bluetooth is) thus allowing others to possibly implement it.

To clarify Firefox is my main browser, but (sadly) for those very specific cases I’m relying on Chromium (WebXR on standalone XR devices, even now Wolvic switching to Chromium as a backend).

It’s an important point as by doing this Google is pushing for it’s own set of technologies and is pushing for it’s own engine which comes with a lot of business (namely ads) related “feature” e.g Manifest v3 that aren’t good for privacy.

That is also interesting to consider on “why” a browser keeps on evolving, i.e having the most “advanced” browsers does give an edge and pushes competition away.