So you are saying that turning a camshaft does not produce harmonic vibrations, I am sure you have turned a cam without being connected to the crank, it doesn't turn smooth, it turns hard till you get over the top of the lobe then rotates on its own till it hits the next lobe coming up.
This action twist and releases the cam and sets up the vibration & the banging back & forth sets up the vibration.
The gears transmits the vibration to the crank, & the crank has it's own vibrations that do the same thing. I'm not saying the gear drive is a bad thing I am saying I would not use one in my engine. You can't convince me that a metal to metal gear drive absorbents vibration better than a rubber belt or a chain. As for a Fluidamper they are only good for a engine running a constant speed. They are always out of balance till they are balanced, and when the rpm drops the fluid is still moving trying to balance, They are out of balance on the way up and on the way down.
Scat crankshaft doesn't recommend them, Ohio crankshaft doesn't recommend them, Eagle Crankshaft had no comment but the guy I talked to did say he has a steel damper on his engine. So maybe you should do some research. I talk from knowledge not from shi* I hear.
Any one can call tech lines and talk about the products
but you need to use common sense, there selling there product!