That's going to be in reference to the RGB camera and the typical use of combining the RGB image and IR for depth. I don't think the Obstacle Avoidance system needs the RGB camera.i'm wondering why the article states this however : Note: Range is very dependent upon the module and the lighting.
We evaluated the IPS with our test unit. The ultrasonic sensor works well and the unit maintained a consistent altitude indoors. However, the camera did not function for positioning and drift was consistent with a unit without IPS. Our consensus is on our 'Beta' unit, the indoor positioning is not yet completely enabled with the firmware loaded.