I'm not sure if this is normal or not. I never really gave it much thought till we recently started potty training. He has absolutely no reaction to horrible smells around him. If he does have Anosmia then that would explain why he's always loved really spicy foods, his sense of taste would be sorta dulled too. Does your toddler react to things that smell bad?
I don't think until a certain age kids can really identify that they are smelling anything that is bad/good or otherwise. My 4 year old will now say something stinks or smells soooo good... but I don't think my 2 year old has ever said anything about a smell (and my 4yo was the same way until maybe the last 6-12 months). I mean, I can be changing my 2 yo stinky diaper and she's completely oblivious to the fact that she's stinking the house up. LOL If it worries you, you can ask about it... but I guess I wouldn't be too concerned if I were you.
Yes, my 3 year old does say something smells bad and can identify smells, and has been able to for about 6 months. He has a sensitive sense of smell like DH, and is sensitive to spicy foods, like kinda freaks out. Strangely, DH seems under-sensitive to spicy foods.