On philosophical note, my mind is also very active at all time of the day. It's natural mode is to hop from idea to question forever. But that's not really how I'd describe it when I'm DMing or prepping something. In that situation it feels a bit more like being led on, or just letting the next thing lead me on. Like a trail of crumbs. My brain or my memory surely is the one to put the crumbs in front of my consciousness, the when I am in the moment, I feels like I'm just following the crumbs and they were there. I never ask myself questions, I just have an answer. It just comes up.
On a practical note, isn't that inner monologue GM bias? Couldn't you say that random tables and spark tables are tools used to rely more on the dice and less on your inner monologue?