in a way i feel your vibe your going towards. And yes, I think there is a valid point saying "you can train creativity".
In theory (this is just the psycho theory behind it all) is that the mind (brain if you will) is divided in to the "logical" brain (right I believe) and the creative brain (left I believe).
and you can basically train your brain what part to use "at that specific moment". Kind of like yoga if you will, but then for your brain.
I had my share of shrinks so I am kind of familiar with this subject. Not saying that I am the expert on brain theory though. But the point your making is valid.
Its quite similar as drawing, and you teach yourself to draw. There are different techniques to draw, but when it comes to the creative process of drawing you can teach yourself to to the creative process. I believe the same process goes with making music. "out of the boxing" thinking is just a "technique" just to be creative. While I am thinking out loud.
Regarding to the myth about having a writers block, I have mixed opinions on this one. Since it kind of depends if you are "willing" to do something creative (as you have described in the video). However, since the willing part is mostly driven by a thing called "feeling", then we get to a point of discussion, I dare not to touch... since I will get in fights with my girlfriend... more or less
Thanx for sharing the vid!