Wow that's some math and science!
What I find amusing, is where he talks about "If you make the core more dense" the ball will rev up quicker.
On it's own, that is false.
"The moment of inertia for an object is the ratio of applied torque and the resultant angular acceleration of the object."
That line there is a fundamental truth.
There are a few points he states after that is in conflict with that fundamental truth.
The first day in a physics class, they should make you learn the following quote.
"It ain't what you don't know that gets you into trouble. It's what you know for sure that just ain't so." - Mark Twain