I hear a LOT of different terminology working with users here from different regions of the world, especially when it comes to components of doors, windows and roofs. I had never heard that referred to as a Stile or Astragal until this thread, only the "Center Post" "Mullion" or "Jamb Brace"
I theorize that my brain will be completely full of semi-useless facts by age 53 and then I'll have to start dumping out old knowledge to fit more in, like... my birthday, or what color the sky is.