Anyone can very easily avoid training on GPL code. Yes, the model might be not be as strong as one that is trained that way and released under terms of the GPL, but to me that sounds like quite a good outcome if the best models are open source/open weight.
Its all about whose outcomes are optimized.
Of course, the law generally favors consideration of the outcomes for the massive corporations donating hundreds of millions of dollars to legislature campaigns.
Would it even actually help to go down that road though? IMO the expected outcome would simply be that AI training stalls for a bit while "unencumbered" training material is being collected/built up and you achieve basically nothing in the end, except creating a big ongoing logistical/administrative hassle to keep lawyers/bureaucrats fed.
I think the redistribution effect (towards training material providers) from such an scenario would be marginal at best, especially long-term, and event that might be over-optimistic.
I also dislike that stance because it seems obviously inconsistent to me-- if humans are allowed to train on copyrighted material without their output being generally affected, why not machines?