it also seems like this isnt under Tabula Rasa effect spell that SE said that sch would get, since in second part of vid the SCH only used 2 JAs compared to 3 in first part.
Based on the visuals, in the second one seemed to be Merton followed by Manifestation (aoe of enfeebling). In the first one, looked like they opened up with "Dark Arts".
Doesn't look like Addendum: Dark was used in either, since that visual has more of a sphere around your body as opposed to the ring of balls like in manifestation.
So there's a good chance that either
1) Addendum: Dark is not required for the ability.
or
2) That it's not required (which would be evident in the fact they used "Dark Arts" in first video.