I would love to have this guy write my security sensitive software.
I used to work with a guy that would review every line of our projects node modules. He’d find issues all the time, so there’s no way he wasn’t pay attention. He also managed to be productive with writing his features. Having that guy on the team was amazing, I have no idea what motivated him to do such tedious work, but he seemed to love it...
Most programmers feel like hobbyists to me, in their YOLO-approach. Your software might ruin someones day, their life or maybe even end up killing people and more people should take that thing seriously. The way your collegue worked should be the norm.