It's been more than a couple of years since Google added a broadcast functionality to its Home speakers, but throughout all this time, it's been an all-or-nothing approach. You could either send the message to all speakers in a home or none at all. Now, it seems that Google is rolling out an option to broadcast to a single speaker.
Several Reddit users, as well as out tipster Brian, report that their Google Homes have started telling them that they can broadcast to a specific speaker. This happens after they broadcast a message, at which point the speaker spells out the tip. It seems that all you have to say is, "Hey Google, broadcast to [speaker name]" and then either say a custom message or use one of Google's default one.
Many of us have wanted this feature for a while, so I tried it as soon as I could. Unfortunately, the command doesn't work for me. Plus, when I try the regular broadcast request, my speakers don't share the tip with me, so it seems that this hasn't rolled out to everyone just yet.
A specific software update doesn't seem to be responsible — my Google Homes are on the same version as some of the Reddit users — so it's likely a server-side update. Also keep in mind that this will probably only work if your Assistant is set to US English.