centroid details seem contradictory

[greggman]

In the GLSL ES 3.2 spec in relation to gl_FragCoord

In section 4.5 it says

If a fragment shader input is qualified with centroid, a single value may be assigned to that variable for all samples in the pixel, but that value must be interpolated at a location that lies in both the pixel and in the primitive being rendered, including any of the pixel’s samples covered by the primitive.

Where as in section 7.1.5 it says

The use of centroid does not further restrict this value to be inside the current primitive.

It seems like section 4.5 says in centroid mode "that value must be ... in the primitive being rendered" where as 7.1.5 says it doesn't.