Kind of. Actually, she ranted at him for a short bit. I agree with you, btw. He moved so fast, I didn't realize till he was halfway there. Frankly, I kind of freaked, which caused a fair bit of tension upon his return. He didn't "get" why(!) His perspective was that he had to act. I conceded it was a very noble impulse, but given the situation, very dangerous. Interestingly enough, we got a note in our mailbox the next day. It was so sweet, I almost cried. I was so worried that we had made enemies.
Oh, I very much do this too! While paying close attention to surroundings. Not in a freaked out way. The alertness heightens my sense of confidence. I also "think smart" about my positioning, casually avoiding potentially problematic areas like recessed doorways. And use a lengthened confident stride, like I know where I'm going (which hopefully, I do! ) and belong there (ie. like a local).

Alertness to these details can really pay off. One time, I was in a city in another country, at night, with my dad and his wife. I was not in favor of strolling around looking for a restaurant. The location was clearly wrong to me. They walked along, talking w/o thinking about it. This troubled me greatly. Older couple, american accent... hello! Way too easy a mark. I saw a guy, got a strong sense of trouble, and said quietly and firmly, "We are returning to the car. NOW." It wasn't a request. They obeyed, w/o understanding, thinking maybe they should just rearrange some stuff in the car (???!!!) There was someone who'd marked them, and I casually noted his locations as we moved. They still did not realize, and I did not want to take time to explain. We got to the car. "Get in. NOW." They didn't understand fully till we had gone elsewhere, and I'd spelled out exactly what happened and drew a map even. The only time they even saw this guy was right as we were getting in the car. Upon recalling his face, location and body language, they finally realized just how close they'd come to serious trouble. It all came down to being alert to details.