The wastegate is central to all four runners. In this case, the runners almost go directly into the wastegate. This prevents boost creep and means faster spool up. It has nothing to do with the AC. The reason you can use AC with this kit is that the manifold doesn't go down far enough on the engine to interfere with the compressor.
When a wastegate isn't positioned properly it won't be able to bleed off all the excess gasses. This can cause boost to "creep" up. This manifold basically eliminates it since the gasses don't even have to make a turn to enter the wastegate.