or is the premise of the question wrong in the first place?

Yes; there are many other examples that could be mentioned. I discussed some of the most ancient ones in this old answer to the question why full plate wasn't developed sooner. Since you're not asking about full plate but just plate armour in general, the Greeks and Romans would qualify, along with the other peoples of ancient Italy, the Celts, and many others. Outside Europe there are also the many heavily armoured horsemen of Iran, central Asia, the Ottoman Empire and India, who were typically protected by a combination of chain and plate.