OpenCV's ORB feature detector tend form clumps around certain areas

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Which makes it necessary to follow up with non-maximal suppression. In comparison Shi-AndTomasi's GFTT behaves very well.

Is this a drawback of the method or I am not using the ORB feature detection correctly?

Here is the code I used for initializing the detector:

OrbFeatureDetector detector(1000, 1.2f, 3, 20);