I guess I would not be suitable for that type of a job, because my sniffer does not work well with a lot of smells, things really have to smell for me to smell them.
Burnt chocolate I have never smelled before, maybe bad cooks have, but I have never smelled burnt chocolate, and acrid, what kind of smell is that? and pungent (indole)? When in school do they make you smell those things?
I'm of the personal opinion that I have a bad sense of smell. If I could do it, you could too.
A lot of the smells require you to experience it in order to relate. I don't recall them forcing us to smell everything back in school. But, the smells are super helpful.
The burnt chocolate one is interesting because I have heard some folks say it smells disgusting. To me, it's just a light cocoa smell. So, everyone's mileage varies.