Indeed. People put that stuff up on the Internet explicitly so that it can be read. OpenAI's AI read it during training, exactly as it was made available for.

Overfitting is a flaw in AI training that has been a problem that developers have been working on solving for quite a long time, and will continue to work on for reasons entirely divorced from copyright. An AI that simply spits out copies of its training data verbatim is a failure of an AI. Why would anyone want to spend millions of dollars and massive computing resources to replicate the functionality of a copy/paste operation?