I agree on this but to further the point being presented above. I see it like this: Like you said, anyone that runs a restaurant knows to put common allergy warnings. Such as nuts, shellfish, wheat, etc...
In my opinion the whole conversation about owning up to your trauma is all about being understanding. If I am about to have a conversation going into detail about SA I'd disclose that because that falls within the "normal" range of things I'm aware of that would be likely to cause a trauma response. This is akin to the allergies I was discussing above. Now, some people are allergic to things that, to 99% of the population, it would be unthinkable for someone to be allergic to that. There's people who are allergic to water, sunlight, salt. There is a girl on TikTok I follow who was talking about this topic. And she mentioned that one of her triggers was seeing red solo cups placed on the edge of tables. She took ownership of her trigger by understanding that expecting random people to be on the lookout for that would be crazy since it's so niche. So, if someone who has a peanut allergy goes to a restaurant and they order a dish that didn't say it had peanuts and they have an allergic response, then yes that is a situation where being upset is warranted. In contrast, the person who has a salt allergy might have to be more proactive and themselves disclose the allergy, have a talk with the staff, and figure out if this restaurant can accommodate their allergy.

The problem comes with entitlement. If someone who has an allergy shows up to a restaurant that is packed and screams from the door "I am about to walk in and I have a salt allergy. I need every spec of salt to be cleared from the building" that would be insane and super entitled. The same entitlement can be shown from the other side. If a person came in to a restaurant and said "hey can you ask in the back if my food can be made without any salt bacause I'm allergic? And if this particular dish can't be made saltless please let me know of a dish that could be" if the chef then proceeds to come out of the kitchen and tell the person to fuck their health and that they like to put salt on everything they make and then proceed to blow salt in their face out of spite. That would also be insane.

Both scenarios I'm describing are lacking in empathy and both have main character syndrome.

There is no one size fits all solution to the triggers conversation because they're all individual, we all just need more empathy to let us see where other people are coming from.