There is indeed a problem of transparency right now. Companies afaik did not release the complete training data set. Might even be intentionally, because they do not want to risk, that they trained it on stuff they should not have had, without building in license and attribution into the output of their models. Or it might be, that they know that to be a fact.

I can only hope, that lawmakers hurry to catch up with reality and impose transparency obligations for AI models.