I don't think there is any truth to this, you play where it is needed for the sound you're searching for, the harmonics you want to emphasize in your chords/lead playing and based on what is naturally more comfortable.
With the bridge and neck being the opposite extremes in terms of sound and comfort for playing, its much more likely that you will gravitate towards one of them rather than staying in the middle, depending on what you're playing. But, I've been playing just over 11 years now, its not unusual for me to be in a relaxed position with my picking hand nearer the bridge but the actual picking taking place closer to the middle pickup, which is what Slash and Steve Vai are both doing in the above pictures.