Scents indeed can trigger asthma attacks, though you can't expect Universal to have to eliminate them. After I had Covid I developed bad asthma and allergies (luckily it is all controlled now) ; anyway, going to HHN last year I was worried about possible asthma attacks due to scents and so just made sure I had my rescue inhaler with me, luckily I never needed it. Personally for me, my worst trigger remains bleach, even a faint smell of bleach gives me almost instant chest tightness.
Certain smells can trigger asthma-like symptoms due to the neurological reasons, a lot of olfactory processing is done in the Insula which also connects to emotional centers in the brain, this is why we can speak of a disgusting smell. It is really quite fascinating.
Did they also not alter the smoke in Transformers because of people complaining?
As for HHN, I have also heard people complain of skin irritation the next day, which makes sense since most scents are based upon essential oils, which can cause some skin irritation.