>to initiate or precipitate (a chain of events, scientific reaction, psychological process, etc.)
"Psychological process," in this case, is what I was talking about, and what I think the original commenter was referring to. "Trigger warnings" aren't warning you that you might feel "anything that will cause a reaction," they're to help people suffering with PTSD avoid having a panic attack.
I agree that the colloquial definition is trending the way you describe, and I think it's irresponsible to just sit and watch it happen without speaking up in favor of the more specific psychological definition.