Confraria - sushi do Mercado

I will not be reviewing the food itself as I did not get to eat it, however, I still feel like leaving a review of my experiance. As a person with a celiac disease, it can be really challenging to travel and eat out. I have to be very careful with what I eat and I need to do all the research beforehand to make sure that the food is safe for me. I found this sushi place on one of the gluten free travel guides online hence I went there to order. The place had multiple options marked as gluten free so looking at the menu, I felt happy. I wanted to place the order and explained to the staff what my disease is, asking them if it would be possible to wash a knife and a cutting board before prepping my food, just to make sure the gluten contamination is avoided. And surprisingly, the chef refused to do so saying that this will stop the whole production... I understand it would be a small pause for them but we're talking about 2 minutes pause, not stopping the whole production... For them, it would be those 2 minutes, for me however it was having lunch or not. Which I eventually did not have as there were no other gluten free options available around. I do not understand one thing, why marking your food in the menu as gluten free if you cannot really assure the customer it is actually safe?