With regards to latency, in Paris the biggest hurdle to increase trafic is people. You can quite literally walk through like on the Japanese video linked. But the vast majority don't.

The way it's supposed to work is that if you pass your card while the gate is opened, it keeps the gate open longer.

In practice most people wait for the gate to close in front of them before reopening it.

I'm not sure why people do fgaf. I think the reason is that this makes you look like a fraudster going right behind a valid passenger.