I was so intrigued with the seemingly conflicting results and experiences that I set up a scenario in PTW v1.21 to test it. I can post the scenario in the evening (USA PST time) if there is interest.
The scenario has the following properties:
Two landmasses separated by Ocean.
4 Civs; 1 Human and 3 AI civs
Human (Rome) and one AI (Egypt) share a landmass
AI (Greece) and AI (Babylon) share another landmass.
The human starts with susbstantially all technologies except Monarchy and Republic. It enjoys an empire of a dozen or so cities, all at pop 12, with sufficient happiness improvements and available luxuries to prevent riots. Each human city has a temple, cathedral, market, bank, and stock exchange , and those cities on the coast have a harbor, and commercial dock as well. The human starts with 1,000,000 in gold and as a Democracy. The human also has 3 modern armor and two battleships. (this set-up ensures substantial gpt income with the science slider set to 0%).
Poor Egypt has one town (size 1) with one warrior defending. It does start with Monarchy and 100 gold.
Each of Greece and Babylon have several towns (size 1) with harbors and possess 100 gold and knowledge of the Republic.
On turn one, the human player contacts Egypt and establishes an embassy. With the embassy up and running, the human enters into 5 separate deals: (1) MPP; (2) RoP; (3) human buys Monarchy for 55 gpt; (4) human sells silks for 25 gold lump sum; and human buys world map for 1 gpt.
On turn two, the human moves the MA into Egyptian territory and surrounds Thebes. A look at the active deals shows all 5 deals with 19 turns to go. The human attacks without a declaration -- constituting an RoP rape and the breach of 4 other deals. Egypt is destroyed ("Good! They deserved it!"

).
In that same turn, one human battleship contacts Babylon and one contacts Greece. With embassies established in both capitols, each of the newly discovered civs are quite happy to enter into: (1) MPPs; (2) RoPs; (3) sale of either Republic or World Map for a gpt payment; and (4) purchase of a luxury for a lump sum.
This scenario would seem to prove that the Arrian Deception does in fact work.
Killer, I would hold off on updating the FAQ until we figure out why we're seeing discrepancies in how the game handles the "unknown civ" phenomenon.