iPhone SMS read status not syncing between devices

SMS (green) message read status not syncing from iPhone

Since iOS26.1, SMS message “read status” is not updated on other Apple devices when a text is read on another Apple device. Status synching works as expected with Apple messages (blue).

I've restarted all devices, reset Send & Receive permissions and logged out of Messages and back in to Messages.

Is this a bug with 26.1 or has a setting changed that I don’t know about?