Ah, good old Mont Joli! I had this particular thing pop up a number of time when I still had staff travel with the annual concessions and, as you do, you make a number of bookings before settling in for one specific flight. For some reason then BA would start sending me reminders for my flight to Mount Joli.

I also had this way back at the beginning of the pandemic when I had to can a (real) flight booking. It's some weird gremlin hidden away in Reservations. Whether it's BA, or Amadeus, or a bit of both I've never understood.