I can’t make that thing change the display (other filters do work), even with just a black-to-white gradient with 15% pure white and 8% pure black, in a 32-bit linear image.
I remember seeing it working in earlier versions, but it doesn’t work on my 2.10.30, 2.10.34 and 2.99.14.
There doesn’t seem to be a bug report about it, either.