But even then, the server should absolutely know (and therefore be trained on) major allergens in the kitchen because its not just the food, its how its prepared.

20 years ago I didn't know, I didn't know that I ought to know. I didn't know that I could have caused that person significant harm. I was a teenager. But my managers absolutely should have known and not put me in that position where I didn't know something so fundamental to food service. We were trained on other things.