Was vdh still detecting video streams on twitch after blacklisting the site ?
If it wasn't l can't see how this would be connected to vdh . Also you want to be blocking ads not disabling ad blockers.
Another option would be to use private windows where vdh is not running.
There is something in Firefox you could check out by opening l think about: memory
Vdh should be blacklisting twitch then see the extensions memory usage. Also compare with twitch not blacklisted . Are there any differences ?