You wrote, "... before the war, all guns made on contract received contract numbers, not serial numbers. Furthermore, the contract numbers all started at the same number..."
I wonder about your source for that info. As I understand it, the customer, not FN, decided whether to have his guns in a separate number series, based on his needs and inventory control. So one order might start with 1, while another might be like the first Dutch order - two thousand pistols but starting at #3000.
The Greek 1926 order, on the other hand, had the normal serial numbers (in the 202xxx-215xxx range) but the Greeks stamped their own control number on the slide.
One thing is for sure. Numbering of the Model 1922 is confusing!
A general note: Before the passage of various gun control laws, factories rarely cared about serial numbers. Most did not put on any and those that did didn't always keep records of them. Factories making military arms (including Springfield Armory) considered serial numbers a means of inventory control at the using unit, not a means of tracking changes or keeping records at the factory itself. FN was no different in this regard, except that they supplied weapons to many armies, not just one, as at Springfield.