There are two (or more) items of intelligence involved. Only one of them was forged. By inserting the forged documents into the pipeline, the French a.) intended that the forgery be discovered, so that b.) it would discredit the other evidence and c.) end up embarrassing the U.S.
The article (and your question) assumes that French intelligence was also the source of the legitimate evidence. That could be the case. But, then again, it may not be. In may be a Frenchman...as distinct from French intelligence.
In any event, we should recognize that, while France is not necessarily an enemy, she is no longer an ally.
Now there's an oxymoron for you.
That much I recognize.