Shirt collars don’t move the way necks do, so it really depends on posture and movement, I’d say my posture was about the best in my day when I was standing in front of a mirror putting the tie on and judging my appearance, and then 20 minutes later I’d be sitting at my desk hunched forward and it would be a lot less comfortable, so I could see it.

Also I remember from hours and hours of starting at old men’s necks in church how their flesh would spill out the backs and sides of their collars while they sat there listening to the preacher.