I believe this is one of those Google “F it I am going to make this protocol my own way without anyone else’s input” which results in security concerns and also Mozilla prioritizes it being a browser more.
Searching serial looks like this is still the case. There are security and privacy concerns over it.
With a password manager I’d argue its better but supports still not all there yet. I am waiting on bitwarden right now to support mull, basically its blacklisted, but it was added in the last 2 weeks so now its a waiting game.