As far as I noticed all of your screenshots had the taskbar skinned.
That is the taskbar skinned by WindowBlinds by the WB skin RND has made the matching DX theme for, not by his DX theme.
All the themes I'd gotten off this site had always done so but it's been a year or so since I've used them.
These would be themes that had a replacement for the Windows taskbar as part of the theme, which when a DX theme has it hides the Windows taskbar. DX has never skinned the Windows taskbar it just replaces it with it's own when a taskbar is part of the theme.