Nice analysis. I've seen rotors on a vehicles braking system rust overnight due to moisture. Hit the brakes a couple of times and it's gone.The trick is to find (ie create) a knife with just minimal surface rust. These sort of restoration videos have been popping up on my Youtube feed, probably because I watch a lot of sharpening videos. I suspect most were intentionally allowed to rust to just make the video. The rust is never very deep and there's no pitting. In other words, nothing like the rusty knives I've come across.