I have always had a bad sense of smell. A smell has to be strong before I notice it and even then, it’s “something”, “bad” or “good”. So, I am ignorant on the smell of farts. For example….
How long does it take for the smell to spread? How far does it reach? How long does the smell linger?
Do you encounter times where people fart people in public places? For example a smell by the canned peaches at the store. How often do you notice these?
Are there different “flavors”? How would they be described? Would you know if it was because they had eaten beans, or it was time for them to go potty, or whatever?
Do people have their unique smells? Would you be able to recognize the smell of farts by your significant other?
When visiting Sweden last year, our hosts of course made sure we (well, I - my wife, conveniently, is a vegetarian) got a chance to try Surströmming. I think they were a bit disappointed that we were unfazed by the smell, but the truth is we were already used to it, because it smells exactly like our dog’s farts. Not an exaggeration - it was an exact match that even made us feel a little homesick. Our dog farts fermented fish gas, apparently.
(For the record, it tastes better than it smells, but I still wouldn’t go out of my way to eat it again. My understanding is that this is a common attitude toward the stuff even among Swedes.)
To answer the OP, farts are just such an individual and variable product of a wide variety of inputs. Diet is probably the biggest factor. As far as individual people having their own, unique fart smells independent of their diet? It’s not impossible but I wouldn’t bet on it.