What is not being touched on here is the that the term " 6 pack" is not the true definition of what is being discussed. The "6 pack" only describes those instruments used in "attitude instrument flying". Whereas a "glass cockpit" concept includes all forms navigation information in the primary display.
Learning to fly the "6 pack" AND the associated navigation information, in the most basic format, non, HSI, omni bearing, and fixed-card ADF, forces the student to have a mental picture of his navigation situation. If you think about some of the questions on the instrument written exam, you will remember that they deal with OBS displays and ask you to orient yourself. There are questions about intersections, localizer orientation and holding.
This skill is takes time and study but once learned and practiced it works wonders when transitioning to glass. It gives the student the confidence to know where he is in relation to his surroundings when the glass fails or his navigation system is imparted in some way.
Knowing you can control the airplane accurately with only basic flight instruments and navigate as well are tools that every professional pilot needs to be able to draw upon. If you are considering a career in aviation as a pilot do not overlook this basic skill. The few extra hours in primary training learning this skill can help save your life and you will have confidence and as the military pilots say, "better situational awareness" or SA.