Au contraire! Formalized protocols on diplomacy date back to the Bronze Age, though the modern procedures of standard practices began to take shape throughout the 1600s, into the early 1700s (per the Digital Encyclopedia of History Project at the Sorbonne). But of course, for any effort at standardization to begin, two things are necessary: some activity, involving diverse actors, which occurs frequently enough that standardization is more than just a waste of time; and, some assortment of pre-existing standards which may be proposed as part of standardization. For example, French became the standard language of diplomacy in the early 1700s, but it, of course, had existed loooooooooong before that point. It was chosen because it already was so commonly used.
In another vein: Tycho Brahe, one of the great Renaissance astronomers and mentor to Johannes Kepler, died, in large part, due to the strict demands of diplomatic etiquette. At a dinner in 1601, he really needed to pee. But, it was a severe breach of etiquette to stand from the table during a meal; by the time he was free to relieve himself, he could not do so, either due to inflammation of the bladder/urinary tract, or kidney stones. Either way, he died, unable to piss for nearly two weeks, all as a consequence of etiquette.
So be assured, that, in the age of sail, etiquette was DEFINITELY well established between any two nations before their representatives dared meet formally. And a well-built fantasy world would function no differently.