You can break your fast as soon as Maghrib Azan has said. But if anyone wants to break his/her fast after performing Maghrebain namaz or Maghreb namaz thats also better.
There is no logic behind waiting for 10 minutes unnecessarily after maghrib azan to break ones fast. As soon as Azan of Maghrib has said no either you break your fast of pray your namaz it’s up to you.