I believe your lecturer is looking at it from a technical viewpoint - as a pilot I go with the pax evacuation theory, because (a) I'm not aware of any procedures to reduce electrical loads during t/o to protect the generators, (b) the gens. would be at high speed at t/o, i.e. most capable, whilst if they did need protecting, the low speed regime would be where it happened. (c) As you will know, eye adjustment to dark conditions takes several minutes. In an emergency, cabin lighting will go down automatically to emergency level as the generators go off line, and evac. will need to be completed in a couple of minutes or so.
Regards - Musang