Billy wanted his neck pickup to have "super deep low end." The Relentless™ Neck does the job with a very low resonant peak, giving all the lower frequencies more depth. The low end carries well even as you play in the upper registers of the fretboard, basically holding the bottom end in a live situation regardless of where you are on the fretboard.
The Relentless™ Neck will work just as well in the bridge position due to its big low-end response. The higher output gives you more options with height adjustment.