Are you sure Dolby headphone is even activated, sounds to me like you may be listening with the EQ settings enabled and the Channel Mixer plugin tweaks but DH isn't activated. Check in the settings for the DH wrapper that the dolby headphone dll plugin is loaded. Some users reported it isn't loaded by default when you grab the preconfigured package, you might have to manually enable it.
This page, check so it's loaded ("location" path will be empty if it's not loaded):
FILE -> PREFERENCES -> PLAYBACK -> DSP MANAGER. SELECT DOLBY HEADPHONE PLUGIN IN THE LIST -> CONFIGURE SELECTED
DH was 100% activated when I used it as it appeared exactly like what your screenshot shows except path was C:\foobar2000\components\DolbyHph.dll to be accurate, but it's the same thing. It's easy to notice since I have a xonar soundcard as reference.