Although this question of focus would be better discussed in terms of neuroscience - in particular the chemistry of memory formation - I want just to share my personal experience.
Back in my undergraduate days, and prior to that, I used to study several hours a day, mainly watching TV simultaneously. I was not aware of many things I am now, so I couldn't figure out what happened when I did play live, or in any situation where my full brain capacity was on the stake. It was a time of mistakes on the stage, of faulty mechanics, of blanks...
Some years after that, my way of studying changed a lot and I must say it changed how much I enjoy studying. Now I don't do anything else, I unplug myself during the sessions (no computer, no phone), and the results are just another league. The most amazing change was the control of a work from its parts to minute details.
Of course there are other things that contribute to this result, but there is a single aspect that is interesting. When I used to study watching a movie, I was able to recall scenes, actors, even dialog lines that ocurred during my practice time when I played the work live. That is, the brain is stimulated to recall, and it fills up with everything available, not with what he is meant to. Now, when I play the only thing that come is the work itself.
Best regards,
Jay.