In HDR video picture mode, the black level is raised unless some form of MotionFlow is engaged. It is as if local dimming is not active for the black portions of a scene. You can test this easily on any HDR content with letterbox bars or a scene with mostly black background. Switch from "Off' to "True Cinema" for example and you will notice the black level lower substantially.
Sony XBR75X940C, UBP-X800, PS4 Pro 5.1.2 System Yamaha RX-V1081 Paradigm Studio 60 V5, Monitor Center 3 V7, Titan V2 Pioneer SP-T22A-LR DIY 15" Sub w/Inuke1000DSP