Maybe that's why shorter men have a stereotype of insecurity. Napolean complex. They are not really less secure, their head is tilted up more often.
I think it would be the opposite. Someone who is taller than you would on average look more like their head is tilted up from your perspective, and vice versa for someone shorter than you.
Only if they're not physically looking down at you, which they probably are.
What if they're looking down at you, with their eyes only? Don't bend the neck?
(I'm going to observe what I'm doing myself the next time I talk to a shorter person :-))