The problem revolves around the fact that the holes in the flywheel are 'clearance' holes & the flywheel is prevented from moving through sheer brute force & ignorance. This is just fine in a stocker that rarely sees 5.000 rpm.

However,...... it would seem that at very high engine speeds, harmonic forces in the crankshaft can be great enough to cause the flywheel to move under the heads of the bolts. Basicly, it moves around the crank just a tiny little bit, within the constraints of the amount of clearance in the bolt holes. It doesn't take much of this to fret wherever the flywheel touches something, like the crank itself, as well as under the heads of the bolts. This quickly reduces the tension, or clamping force of the bolts & allows even more movement. If left to its own devices, the holes elongate, allowing the flywheel a good runup at the bolts untill they eventually shear off.

Using tightly fitting dowls removes the job of preventing flywheel rotation [around the crank] from these bolts in clearance holes.

It's a bit like birds & airplanes. Birds use wings for motive force as well as flight. Airplanes separate these functions & use wings for flight & engines for propulsion.
Dowels do the same job of separating tasks.
The bolts hold the flywheel on, while the dowels prevent any movement.

This method works, & works well, however it addresses the SYMPTOMS, & not the CAUSE. The harmonic balancer addresses the cause.