Is hairline chatter related to metal flow?

I think a sintered planchet can also happen in an annealing drum?

 

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I do not believe this is likely the same thing. I'm not certain what it is because "burnishing" which is done to many planchets including both mint set and proofs uses spherical "ball bearings". It's entirely possible this has changed or this is related to a different process. While the surfaces could get uneven they tend to be polished more than eroded.

I know nothing about the machine supposedly in operation to bang up regular issue planchets but it seems more likely they'd be tumbled with odd shaped steel. If you look at an incomplete strike you can see how scatches disa[ppear under the strike. These scratches don't look like they came from the process you describe.

 

The source of the scratches is from the annealing process and subsequent washing we already determined that with a call to a former mint employee or you can read about it on the ikegroup.com. The struck half of the off center coin is smooth and flat because the pressure from the strike makes the metal flow and essentially melts the surface of the coin and allows it to take on the shape of the die. The article i posted describes the minting of gold and silver business strike coins.