Why are offset lead-in arcs used?
Image source: Google Earth, showing offset lead-in arcs.
There is little literature on the subject matter. I did research it a while back but I lost the PDF's, and videos. Research was inconclusive.
But I did learn that they guide only one aircraft type—selected radius can only accommodate a single wheelbase, radii vary. Initially I thought long airliners (A346, B773, and so on). But watching videos from observation decks in airports, even a 777-300 doesn't follow it. Whether taxiing in or pushing out, it wasn't even close to the line.
So if only one wheelbase can benefit, and it is not long airliners, why use it?
Image source: Google Earth, showing non-offset lead-in arcs.
Image source: Google Earth, showing straight lead-in lines.
All images from KJFK.