I don't think that's true.
Usually you need to think a lot about something before coming up with "the right" thought(s).
> Every thought you’ve ever had is essentially a procedurally generated prompt based on your biased models.
That may be. But the interesting part is that those models change as you use them just by using them.
How long did you have to think to produce that thought? Or did it just pop into your head instantly?
The point is, you cannot think of an upcoming thought, before you have it in your head. Otherwise you would be seeing into the future.
What you are talking about in your comment is reaching a conclusion based on previous thoughts. Yes, often we link our thoughts together into a narrative or a conclusion after we've had the thoughts, but the thoughts themselves? Those seem to come out of nowhere.
That's true even for very simple things like motion. You can measure things in the brain before those things become conscious thoughts. (Those experiments caused by the way a lot of fuss whether we have free will or are completely predestined in all we do; but that's another topic).
The consciousness only observes a small portion of the thought process. So for it a lot of thoughts seem to come out of nowhere. But the unconscious parts of thinking are very important to the whole process and it's outcomes. I think nobody disputes this by this time.