It's good that's changed, but that wasn't the case the last time I saw any kind of news about Signal (maybe a few months ago). It would serve them well to publicize these changes.
This is a classic example of what I think we should call "The Message Board Apology": "I was wrong about everything but in a way that makes me even righter."
A common occurrence here on HN
The Signal desktop client as far as I know never was tethered to the phone (during operation, signup and getting the desktop one connected still requires a phone). you might be confusing it with Whatsapp's?
The desktop client worked the same way (untethered, after initial setup) a few months ago as well.