Yes, that would be concentric infill used for an external infill (top or bottom areas of a print).
That option is in the INFILL section under EXTERNAL FILL PATTERN. If you select CONCENTRIC you get the pattern you saw if printing a rectangle.
The pattern you see depends on the outline of the external layer. With a circle outline, the pattern would be a bunch of circles inside each other. With a square, a bunch of squares, etc. It can create some very interesting patterns for more complex shapes.
Be warned that the CONCENTRIC pattern system sometimes leaves a few holes in the print. It can't always fill things all the way because of how the pattern is laid out. So always inspect the G-code appearance before printing to be sure you don't see holes. If you see holes, you can try playing around with EXTRUSION WIDTH a little to get things to fill all the way, which is sometimes possible, but not always, depending on the layer's shape.