Comment by frankhhhhhhhhh

The reason to have a map on screen when descending is to anticipate upcoming bends. This helps you to take the best line through the apex of the corners. Also mountain descents will regularly throw you very tight, and sometimes blind corners at random, and the best practice to handle these without going off the road is to brake hard enough to scrub off some speed before you begin your turn, then let go so you're not braking while turning. Navigation prompts will not show this because they are not turns.