The feature needs OS-specific work, so one platform had to be first, and for whatever reason MacOS was chosen. It's more useful to have it working reasonably we

The feature needs OS-specific work, so one platform had to be first, and for whatever reason MacOS was chosen. It's more useful to have it working reasonably well on one platform, to get feedback on the feature, than to have it in a bad state on all platforms. So, no need to over-react. If Mozilla decides it's worth shipping, they'll port it to other plaforms.