Extremely weird issue with Zidoo and black clipping pattern test

I had my TV calibrated and I was just checking out some black pattern tests. I found the weirdest thing.........with every other device, if I jack up the TV Brightness (just for fun), I can see all the way down to like level 2. If I do the same with the Zidoo, I CANNOT see below 16 (which should be the black point in Limited SDR), even with TV Brightness on 100. Why is this happening? Obviously I wouldn't keep TV Brightness at 100 but why is the Zidoo incapable of showing anything under 16 while every other device can show it if I raise brightness? Is this intended?

Other devices that show below 16 with full TV Brightness (black level) are the TV Internal Player and Ugoos AMb6+. Zidoo does not show below 16.

Just curious - does the zidoo cut off everything below 16 because limited range is 16-235? If so that makes sense. But then why do my other limited range devices show below 16 if I turn the brightness up?