[Wowfunhappy]

There is no logical connection between moving a pencil to construct letterforms and deciding what you want to say. They have traditionally happened together, because before computers (or to some extent before typewriters) there was no better way to do one without the other.

[bigbuppo]

You think about words, those words become physical movements, those physical movements create a mark on paper, the brain reads those physical marks, which causes it to think about words, which become physical movements, which become physical marks, which are read, which causes...

I'm sure if you drove the unicycle through a trough of paint and then used it to make words you'd have a similar experience.

[odkckwjckw]

Yes, there is. The act of writing requires you to think about the words, focus on them, think about their shapes and how you must move your hands to form them. You are actively and methodically engaging with the vocabulary as you write the words down.

This is nowhere near the same as doing to completely unrelated activities at the same time.