Aw, looks like I'm late to the party. And I registered just to speculate on the center hex, too.

toma02 covered it already. Parson could see all the enemy units and knew that they could hit the rear of the "fort", so he originally planned on spreading the B dwagons out and hoping that 4 would be enough to survive. But then Wanda pointed out Ansom had no Lookamancy, so rather than gambling on a stack of 4 being enough he decided to fake Ansom out and hide the wounded dwagons elsewhere, sacrificing a stack of 3.

One interesting thing though: it looks like they can't see the dwagons at all without actually moving a unit into the hex they're hiding in. So even after they kill the 3 bait dwagons they won't be able to see the center hex until they try attacking. Will the alliance be smart enough to use another sacrificial bat before charging in with everything they have? Ansom and Vinnie both seem to be pretty reluctant about using bats that way, and they're already pretty sure of what they're facing in the center hex. If there's not actually anything there, they won't lose anything... except moves. The only units capable of attacking the center hex are fliers and forest units, and getting into the center hex is almost guaranteed to use up the last move of whatever Ansom sends in. So suppose he sends in his remaining forest units with Jillian and the Archons as air support, only to find nothing there... now all his most valuable air units are cut off from most of his air power at the start of Stanley's next turn, with ALL of Stanley's dwagons at full health and in position to attack.