Is this flywheel made out of metal, like most flywheels? I don't understand the diagnosis? What is a "broken" flywheel? I've never heard of a "broken" flywheel. I've seen smoked clutch discs and pressure plates, and over-heated flywheel surfaces that are stress cracked. I've heard of clutch discs disintegrating from over revving. This may be abuse, but there is a good possibility it's a defective part. To actually break flywheel, I'd think it would take incredible force. There's more to this.
The dual mass flywheel construction relocates the damper from the driven disc to the engine flywheel. This repositioning dampens engine torsional vibrations more than is possible with standard clutch disc dampening technology. Which is why they should be replaced and not resurfaced like in the ole days.
There is a friction ring located between the inner and outer flywheel that allows the inner and outer flywheel to slip. This is designed to alleviate any damage to the transmission when torque loads exceed the vehicle rating of the transmission. The friction ring is the weak spot in the system and can wear out if excessive engine torque loads are applied through it. The system also has a centre support bearing that carries the load between the inner and outer flywheel. The system is also fitted with damper springs to absorb shocks.
What's going on is since the dual-mass flywheel isn't dampening the vibrations going to the tranny. It then gets amplified and broadcast to you ears from the tranny. The stock flywheels are exactly weighted and when they get resurfaced it takes away from the original mass, that's what makes them no good for dampening the noise anymore.
Getrag makes their six speed clutch assemblies backwards from normal clutches by using the dual mass flywheels and solid disk, whereas normal clutches like in the RX7 5-speeds are a solid flywheel with a sprung hub disk.