This is pretty much what happened. Both lanes were open and said they were open, the lady in the ticket office on our side waived us up because there was literally nobody else in her line. If anything, that should just be a gentle notice to, say, half the people in the other line that 'hey, there are 2 lines, some of you can come over here like this couple that apparently can read and process information at the same time!" but instead they got grumpy that someone got to the window faster than they did.
I was pretty steamed though- to the extent I called the group "a bunch of f-ing idiots that can't read" to their faces.