If I see sesame in an ingredients list, and I discover that really means “we don’t deep clean the oven conveyer after cooking sesame products”, I think I’d feel at least a little tricked.
Or it could mean the conveyor next to it uses lots of sesame oil and they can’t guarantee every single particle stayed in that belt.
Or it could mean the conveyor on the other side of the factory is and they don’t want to risk it.
Nobody knows the specific reasoning a company has for adding it in unless they had insider info from the company itself. Everything else is pure speculation.