I can't answer that.
I dress at dinner a la Trip - but I don't call that formal - I call that smart casual.
I think maybe Europeans have a different definition of Formal?
On my HAL cruise, I was invited to the Capt Cocktail party, don't know why, dressed a la Trip and stood out like a sore thumb because I was overdressed! After a few cocktails, I couldn't care less but I felt really uneasy. So I am really confused now.