edge rule comes from program synthesis simplicity prior

+edge (what o1 did in guess 2):
if (pa.x == pb.x || pa.y == pb.y) connect;

-edge (what o1 did in guess 1):
if ((pa.x == pb.x && sort(pa.x, pb.x) == [0, width - 1]) || ...

-edge *feels* more intuitive because it aligns…