Many times when I'm eating a salad for lunch and DS is sitting next to me, he has said he can smell it. He wrinkles his nose and waves his hand in front of his face.
It's a green salad, little man. No tuna. No smelly cheese.
Perhaps he's just very attuned to his sense of smell and that is what is driving this. I wouldn't be surprised. My dad is very sensitive to smell and I also have inherited that to a degree.
Hum...
Since food likes/dislikes are attributed quite a bit to the sense of smell, maybe there's a study somewhere that has given food scents a rating on a scale? It would make sense that a person with an aversion to mushrooms (yuck) would also perhaps not like a similarly scoring food.