Article fails some quick tests.

To have a $2K/mo payment on a standard 30 year loan with $360 of the first payment going to principal requires a loan amount of $343,477 and an interest rate of ~5.73%. Strange numbers but it's just an example.

The first real problem is that with such a loan the last payment will have $9.50 in interest, not $60.

The major problem is that an extra $2000 paid in the first month reduces total interest paid by $8940, not $60.

The root of the problem is the article's assumption that "...any extra payment applies to the last payment due." Some loan contracts may be so worded, but the more common practice is for additional payments to reduce principal immediately.

Given those issues, I didn't look at the rest of the article.