1. I've posted several videos of scenes where the anime has neglected to add electricity to scenes where electricity was present in the manga. Not only that, but electricity doesn't matter for this concept drawing because, as you can clearly see, young Gohan doesn't have it in the drawing, despite the fact that SS2 Teen Gohan has electricity. Only an idiot would claim SS2 Gohan isn't present in that picture at all, yet no electricity is found anywhere there.
[video=youtube;YmvRJOHMhaw]https://www.youtube.com/watch?v=YmvRJOHMhaw[/video]
This video extensively depicts Goku and Vegeta lacking the electrical aura, though they fought in Super Saiyann 2.
2. The movie is non-canon, therefore, inconsistencies are to be expected. The movie also has a faulty timeline, Shenron grants a wish without showing up, so the fact that Gohan went SS2 so quickly doesn't have to be accounted for, as it can just be considered the result of non-canonical inconsistency and is therefore excused.
3. Akira Toriyama himself has lent credibility to the Daizenshuu, as he has commented that it contains things he himself had forgotten about the series, and expressed gratitude for the Daizenshuu, meaning, despite it having other writers, who by the way were working Toriyama on the original manga series, Toriyama has approved it and its content.