Seems logical that the two walls act to funnel people down towards the opening - a 90 degree-wide corner exit is halfway between a 180 degree-wide funnel towards a single door in a wall, and a 0 degree wide corridor that leads to a door.
Likewise the 'obstructed' wall entrance just turns into two corner exits, side-by side (I imagine the scenario doesn't work out well for the individuals caught directly behind the pillar, as the flow past each side of the pillar into each exit zone prevents them from getting into either flow effectively).
I can see how 90-degrees corner helps funneling. I'd like to see an experiment with a 50-degrees angle, I'd assume people/ants crush each other, because they think it's fair to remain shoulder-to-shoulder with the same people.
And thus it follows that, by repeatedly adding pillars and doubling the number and halving the size/spacing at each step, you can approach infinite throughput!
Likewise the 'obstructed' wall entrance just turns into two corner exits, side-by side (I imagine the scenario doesn't work out well for the individuals caught directly behind the pillar, as the flow past each side of the pillar into each exit zone prevents them from getting into either flow effectively).