I'm not clear on when you're noticing these 'system off to save battery' messages. Are they on the sync screen when you return to a locked car?

True fact, iron rusts! It'll just be the direction of the rain, since you last drove it, was hitting the offside and not the nearside.. Nothing to worry about.

Physically the engine will be the same but the control software may well be different. Maybe ask the dealer if your car is running the latest PCM software after mentioning the difference you experienced?

The hybrid Puma has two starter motors, a 12 volt and a 48 volt. The 12 volt is for first engine starts. The 48 volt is used for stop/start. What you describe sounds like the 48 volt went faulty as you stopped at the lights, requiring the 12 volt starter to restart the engine. Has it happened again?

So the dash cam was keeping the vehicle 'alive' and after period of time the 'system off to save battery' message was coming?

Heavily depleting a lead acid battery is not a problem so long as you recharge within a day or two. Any longer and they start to sulfate, shortening their life.