You could reason that if you engage the brain with something, then it cannot do another thing at the same time. So if you engage the areas responsible for creative thought processes, these areas will not be available for other tasks.

Obviously this might not be the same for everyone, I'm just cautioning people and urging everyone to do some testing.

Another example is that many people (including myself) can't dictate, for the same reasons. In my case, whenever I use dictation, I later go back and re-read what I wrote and it is always disappointing. It seems the areas of my brain that process speech are also needed to form thoughts into sentences and I just can't do both well.