I don't understand what happens in the beginning of this video, it looks like no total traction in wheels. But supposedly total traction is automatically activated when needed, even if you don't lock it. But it seems only 2W.
Hard to say. You can lock it in 2wd. Also, some modes allow a bit of slip could have guessed wrong in auto or been in one of those modes. Although it does look like more slip than in other demos. I'm inclined to go with the first scenario.
In my experience, the modes have a dramatic effect on slip allowed. It looks like the drivers front tire is slipping, but there is drag there as it's not in the air (and it's moved off the totally free roller). Depending on the mode I've selected, it slips a different amount on a _slightly_ grippy surface. For instance, sand at the bottom of a slick rock climb: do you want it to churn a little sand or do you want a weak wheel getting nothing at all. From my own tests, giving it more power usually produces the desired result when traction is not perfect.