Remove ground plane in HDRIBackdrop

Surprised this doesn’t seem to be a toggle option in the settings. Also checked the documentation.
I need to removed the ground plane entirely when using the HDRIBackdrop plugin.

Right now the bottom half of any HDRI image I use is shaded darker. In the attached I am using the GrayLightTextureCube image to illustrate the issue.

One workaround is to us a very small size like 100 and enable ‘Use Camera Projection’ however I need a much larger size 1-10,000.

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The HDRI doc page instructs in using ground plane to get more accurate lighting. What is the ground plane replaceable with?