pretraining isn't unsupervised, it is self-supervised - meaning it is moderately more scale limited.
Whereas self-supervised, allows learning without explicit annotation of data ; but it doesn't matter if the models already trained on the entire Internet, and it's not like a game where it can come up with effectively new training data for itself?
Unsupervised is something where there is no intrinsic reward signal. In pre training, predicting the next token and seeing that it matches is a reward signal, hence it is self supervised.