Looks like it will just play normally on desktop but the queue view is empty. It will only show what was played recently.
I tested this on two different PC's (v5.30.320)
On mobile it works fine. I can see the list of songs,  and btw, the recommendations are spot on!

The screenshots in the official announcement only show how it looks in the mobile app, so it is possible that the developers only implemented it there yet, but accidentally already show the feature (formerly known as Track Mix) in the desktop app and web player. Or it is a bug, because it should also work there.

OK, in the meantime I got a new desktop version 5.30.320, and it works there as well as in the web player. But you have to directly click on the play button which appears when hovering the album thumbnail with your mouse. If you click on the track title, it will only open the related track page which of course only plays that one track then.

Or do you expect to see a full list of upcoming tracks in the play queue perhaps? That does not happen with any mix generated by an algorithm, you can only see the currently playing track plus the previous tracks of that mix:

 

Or do you expect to see a full list of upcoming tracks in the play queue perhaps? That does not happen with any mix generated by an algorithm, you can only see the currently playing track plus the previous tracks of that mix:

 

Yes that is what I meant. I see the track list in the mobile app though when I use this feature.

I was wondering the same thing and then figured it out. Whether on desktop or the app, you need to click on the album icon (the picture) and then it will start the mix. The featured song will always be first on the mix.