It's true that they were coerced, but part of the narrative that explained away the coercion was the claim about manipulation on CEXs. If this claim can be proven false, then witnesses can't kid themselves that they are protecting poor marginers who are being unfairly attacked. And marginers would have to consider more strongly the damage they were doing to the ultimate value of BTS by such an obviously corrupt action.

Averaging over a time window might work, but it risks a case of insufficient collateral in the case where there's an abrupt drop in price. Margin calls have to be made rapidly in such cases.