Completely disagree.
For the restaurant in question it is a major national chain, so indeed it is harder for the server to have this knowledge on every dish, but at least a book of allergens... really the company should have this available in a friendly manner online.
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.
The staff should be able to answer questions about what ingredients are used in the kitchen and in specific dishes. but they shouldn't be responsible for answering the question as you posed it : "is this safe for someone with celiac" ? Safety is up to you to decide, as only the customer knows how sensitive they are and what the reaction will be.
Celiac is a specific condition, not even an allergy.
If someone has celiac, they cannot have gluten without bad consequences.
Being able to serve someone with celiac means the kitchen has deliberately chosen to do so and have procedures in place for doing it.
Things like changing out gloves, cleaning surfaces or having dedicated space.
This also means knowing what cannot be made safe, which often is things like french fries because friers tend to be shared with gluten products.
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.