I was on that same flight.
I surmised the kid in the green uniform who was wrangling the lines wanted to make a separate queue for those pax that needed to pay a reciprocity fee, but when I asked if Canadians should join the new line he was making, he said, "Americans only".
I stayed in my (slow) line until I made it to the top of the escalator leading to the immigration area when he saw me again and said, "Canadian? Over here."
50 minutes later, I finally cleared customs. Viva EZE...
