No, even under such a restrictive license (which I think the GFDL is?) there's no argument.

Their copyright was not violated by anthropic downloading the books, because anthropic had a license to do that.

And their copyright was not violated by anthropic training on the books, because the court found that no ones copyright was violated by doing this. Antrhopic didn't need a license to do this. So the restrictive terms of the license can't prevent it.

I mean they might have an argument for compensation based on "well the settlement Anthropic agreed to didn't exclude us even though they didn't violate our copyright"... but just for the compensation outlined in the settlement.