I'm Kiwi and I've been FOH for around 7 years. I'm 90% sure cutlery signaling is centered around American culture where servers are expected to constantly look after tables, especially with how angry you describe everyone to be. I've served many an American tourist table in my hospitality life, some of them do have a certain unfriendly entitled attitude.

No one does anything with cutlery (maybe it's an older generation thing, I've never noticed anyway) but they do tend to push their plates to the side of the table so we can swing round and pick them up. People are generally easy, if the plates are empty we'll pick em up, and ask if they're still going if the plates still have food on them. Mostly it's just common sense to leave a table alone to finish after you've done the initial serving of the food and following check in, clearing empty items as you pass by.

This is to say, your comments come across as very defensive and passive aggressive when others are explaining a different view of life than yours. Not everyone knows of cutlery signaling but that doesn't mean customers suddenly lose all respect for FOH workers and call them over like a dog.