Another factor could be the cartographer's license. That part of the state is dotted with a huge number of pond-like kettles (ponds resulting from ice-calving during glacial retreat). Like Pinelands spungs, mapmakers for convenience don't always add small ponds as important landscape features. They have to draw the line somewhere.
I provide as example the Skating Ponds (Ponds A & B) in the woods near my place. Both are mirror images of each other in size, depth, and hydrofill.
Views of the Skating Ponds (A & B) as depicted on four different images from NJPineBarrens Maps.
Pond C is a natural spung. Pond D is a borrow pit.
(from top left: 1931 aerial photomosics; modern base map, modern USGS topo map; 1889 USGS topo map)
I've taken pond outlines from the aerial record and transferred them to other maps. The fit is poor. Don't put too much faith in the accuracy of water features shown on these maps. Pond C has a way longer period of hydrofill than Pond D, yet does not appear on any map record I have ever seen. Only geeks like us care.
S-M