@Elijah F. I think where I missed you is that the key component to all of this is time. Compound interest is calculated on a monthly basis and amortized in such a way that it is paid at the beginning of the life of the mortgage. Simple interest is calculated daily based on the remaining balance. Either one of those forms of interest is irrelevant when thinking in terms of time. Yes, over a long period of time the difference between the two can be negligible if you are making minimum payments. The key to what we do is 1. the mortgage is eliminated, 2. what we pay in simple interest is much cheaper allowing us to affect much more principle every month for the same payment, 3. and the biggest money saver is the fact that having the ability to pay down principle much faster dramatically reduces the amount of time to pay off the debt. 5-7 years of simple interest vs 30 years of compound. It's all about time. Much less time having to pay and a lower interest rate means exponentially less money paid in interest. Simple vs compound interest isn't even in the same ball park when it comes to time. In my case, it saves us more than $300,000 in interest payments and 23-25 years less time stuck in a mortgage.
There are other ways to do this same thing (double payments, paying down large chunks of principle using smaller lines of credit, etc) this is just the quickest most direct means to eliminate as much interest as possible.