Perhaps to convince unbelievers, you could try getting your students to sit in their normal seating position and see where 45 degrees from the horizontal is.
To do this, sit in the seat, stick your arm out level in front of you, then straight down beside you, and then point to the position that's half way between the two. For me, it's a couple of inches in front of my feet.
Then look at where the top of the instrument panel is with reference to the horizon; it won't be too far down. The angle between your eyes and the horizon is basically horizontal, so you can judge angles between your eyes and aim points on the ground with reference to that.
Then adding in the illusory 'steepening' effect that is brought in by the decelerative attitudes you get into while approaching (can be quite exciting on a dark night), and the whole picture should make more sense.