The only workaround that I have found it to disconnect the watch from the phone. Play music on phone and then connect the watch again. The ongoing icon notification does not appear (until the corresponding app is opened on the watch).
I had raised this with Support last year. No response yet. I suggest you also send send an error report.
Just to elaborate on the workaround, you don't have to keep the watch disconnected all the time. Disconnect the watch before playing music and after you start the music on your phone, connect the watch again. Note that the moment you pause and play again, the icon will appear on the watch.
Sunday - last edited Sunday