Funny how every car from the inception of the internal combustion engine till around the mid 2000s had solid flywheels and they didn't rattle.

I have a lightweight flywheel on my rally car, solid, it doesn't rattle.

Secondary and trinary harmonics are present in all rotating masses, the 4 cylinder engine is horrific in terms of dynamic balance, but, there should still not be significant noise unless tolerances are wide in the transmission, the noise will not be from the engine.