Of course, Antoninus, but CDG isn't Paris, and JFK isn't New York
Except that Concorde PAX were paying a small foturne for their tickets, and could roll up to check in with minutes to spare, go through the express channels and stroll on board, or get pampered in the Concorde lounge. Much like some airlines do now with limos and bag checkins from your location for first class travellers. Regardless of how long it takes at each end, it still saves hours.