I can see this in some of the people I have trained with at my club. It is a subtle 'hardness' in their character. They can be very nice people but they are under no illusion about what would be required in a life-threatening situation. Others are internally 'softer'. I sense hesitation and self-doubt in these people. I'm not just talking about beginners either.
I wonder, though, if your guesses are right. It's not unreasonable to make the predictions you are based on what you see, but I'm not sure it would always be right... people may seem, as you put it, softer or harder _because_ they are not actually in a life threatening situation. E.g., a person may be more confident and aggressive because they know they are not in real danger, likewise a person may be more hesitant about causing harm because they know they are not in real danger.
I'm not sure, though, how to know what the real reaction would be, or how to change it.