At this scale, that kind of thing is not really a problem; you just dump all of the data you can find into the model (pre-training)1. Of course, the pre-training data influences the model, but the reinforcement learning is really what determines the model’s writing style and, in general, how it “thinks” (post-training).

1 This data is still heavily filtered/cleaned

This isn’t quite accurate. Data weighting is quite important in pretraining.