Just because there is a term for it doesnt mean the idea holds water. At this point pretty much any idea has a term associated with it, but that really means nothing. There are so many completely BS ideas out there with associated terms.
And I know that we think when we are dreaming. And I believe that you may randomly dream about something that has a base in reality.
What I am skeptical about is the ability to go to sleep and control your dreams to the point where you can solve a problem (such as math and science) which you cannot solve while awake.
And as far as the term "sleeping on it", it is usually said when making a decision. And Im pretty sure it is used because sleeping clears your head allowing you to think more clearly.
Anyways I wont continue with this, like I said everyones entitled to their own opinion.