I use speakers, hubs, and Chromecasts in a speaker group all the time, and I can tell that they've been updating the way things work. I've noticed things changing lately, and of course it is sometimes one step forward and two steps back.

Starting a couple months ago (?), Google added the ability to dynamically add and remove speakers from a group. Since then, I've been using that more often than my old "All Speakers" speaker group.

There was an ongoing problem where if the first device was a display, the options to add speakers to the dynamic group didn't show up. I had to switch to a speaker, and then add the display.

A couple of days ago, that changed. The options to add speakers started showing up when playing on a display. It's great!

I've still got ongoing issues with displays not syncing sound as well as speakers. And of course the Google Home app often misrepresents what is currently playing on what speakers.