I was wondering about that too. I once did the same thing. Went to gate 35A instead of 35B, scanned boarding pass, a person even looked at it. Nobody noticed until I saw the sign right above the door with the gate number so I turned around. What are they scanning and what are they looking at?
This is second hand info, so I can't personally vouch. But I heard the scanners at gates with multiple jetways (for example 35 A and B) have software that is set up to accept tickets for both flights. Not sure why you would board both flights concurrently, but may that was a desired feature.
There is also likely a human error component. When you make someone manually scan 150 people they stop paying attention. They should have some kind of error message, but if it looks like other error messages (like the ask about emergency exit message), it's possible the human confused the error and cleared it.
In some airports, airlines are essentially leasing gate space from the airport and any software the airline wants installed on the gate computer has to work in a very fixed set of constraints.
The shared gate agent computers are built from an industry-standard OS image (8 years or so ago this was Windows XP SP2, and not SP3, never SP3).
> When you make someone manually scan 150 people they stop paying attention
Bingo. This is not really a job that people, in general, are any good at. If there was an automated turnstile that didn't suck, that'd be a great place for one, so they could focus on the exceptional cases instead of being lulled to sleep by the happy path.
