[Sirrotica]

It's the stack up of tolerances that would need this, the same as starter to block shims. However whenever parts are machined, or exchanged, the factory window of tolerances will no longer apply. I previously mentioned the shim is to make adjustments in lateral placement of the flexplate in relation to the crankshaft. The OP shows the shim in his pictures, so we can assume it was installed as the parts were assembled.

I have inadvertently left the shim out on the crank flange to flexplate, without negative results. Doubtful it's going to impact the noise that the thread is about.