I tend to agree. To me the preeminent proof of a pre-trib rapture is Christ's teaching of imminence. Once the Anti-Christ is revealed and so forth there no longer remains imminence and we can start to calculate the days down.
So to my thinking the Gog/Magog war has to occur either after the rapture or simultaneously with it so that Christ's teaching 'no man knows the hour' remains intact.
If the rapture were to occur after this war we would know that the rapture is coming and again begin calculating the days down. So there goes the 'no man knows' teaching.
Just my thoughts.