Thanks for the lesson!!
No reason, that is, except native stubbornness, tradition (the CBT trading hours go back for decades, perhaps even a century), and the attitude of ''not invented here''.
Believe me, you are hardly the first to have been a bit confused by the current situation on openings/closings/names of sessions/etc., for which the only proper adjective is ''goofy''. You ought to see the confusion among brand-new broker trainees -- now THIS is the definition of ''Chinese fire drill' !