https://www.dropbox.com/s/sjtjilffjvtdu ... .capx?dl=0
They do receive the broadcast, but they do not run until you focus the tab again.
Try downloading the example capx, preview, duplicating a few tabs. On the host tab, click anywhere to send the message to change layouts.
On peers, they will receive the message, wait 3, then change layouts.
You can switch to each tab to see that they all got the message to change layouts, but don't start their 3 second delay until the tab is active.
In the event where your layouts have different event sheets, or when you send multiple messages in the same frame (before going back to the peer tab to process the original message), you may end up with issues.