Really, that is an ingame quote from a diplomatic message. It does not have to represent the reality. And I know that Rheinland has other means of getting Niobium (by third parties). So... ehm... I don't know what your problem is, but since my statement is ingame, it can be countered ingamely.
And: Of course using resources as leverage is something the IMG does. And since we sacrificed our best trade route (T23-New Berlin) for that conflict, we expect some reaction to it (because it is mainly IMG who does this run). If IMG suffers economically, I can expect the opposite side to suffer, too. =)
IMG does not flatter itself to be able to topple houses by Niobium embargo. I never stated that OORPly, I don't believe it OORPly, but of course I can state it IRP.
But resources have an influence and they must be used as leverage in a standoff. That's why I am doing it.