Mozilla's argument isn't that you'll be tracked or fingerprinted. It's that you're too stupid to be permitted control over whether or not you want to allow access to devices you've connected to your machine. Rather than work to mitigate those risks, they've decided to hobble the utility of their browser.
Personally, it would make flashing ESPHome devices much more convenient. Not having to switch browser for a start. The ability to plug a board into whatever PC on my LAN and just flash it, without having to install and maintain the entire toolchain is nice as well.
A few of these are aimed at the education sector, removing a some of the significant barriers faced by educators that would otherwise have trouble getting the software installed and keeping it updated.
In one of the discussions, someone was using it to help dental offices retrieve data from some specialised hardware. Browser support dealt with similar concerns of how to distribute the software to non-technical clients and keep it up to date. It was also something their clients understood, rather than something new.
What is the justification for making everyone's browser able to "read from and write to serial devices"?
https://developer.mozilla.org/en-US/docs/Web/API/Web_Serial_...
I know it is really for user fingerprinting but what is google's overt justification for pushing it?