Having written MQTT bindings before I know what is possible and how mqtt works in depth…
I don’t believe it is possible to choose what is and what is not retained, probably only possible if a device connects twice to the broker with different connection settings. I could be wrong but it would increase the complexity and resources on the camera. So having all messages as retained is IMHO correct. When openhab connects to the broker it can choose to have a ‘clean session’ where it does not get sent the previous saved states, or to get sent all the states by not using a clean session. Not sure if the mqtt binding gives this option but it is a solution and is explained here.
A dedicated binding that receives all the states and can then filter through and make smart choices based on what the author has written is the better way forward. By not having a dedicated binding and by using a generic method, there is a trade off.