IMHO, we would be splitting hairs debating the 'big box' panel ground bars.
I see the wording within the NEC as a piece of copper, or aluminum that has three (3) dimensions; thickness, width, and an assumed length. Yes, the 'length' is not spelled out in any minimum dimension, but I consider it assumed.
There are formulas to determine amperage ratings for buss bars, and ground/neutral termination bars.
I think of this as attempting to terminate a GEC/EGC that is of a larger AWG than the max that the termination bar is designed to accept.
As Niko stated, I agree with the last scenario.
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John