What you said makes a lot of sense. But here's the catch: it assumes OpenAI checked the licensing for all the stuff they grabbed. And I can guarantee you they didn't.
It's damn near impossible to automatically check the licensing for all the stuff they got she we know for a fact they got stuff whose licensing does not allow it to be used this way. Microsoft has already been sued for Copilot, and these lawsuits will keep coming. Assuming they somehow managed to only grab legit material and they used excellent legal advisors that assured them out would stand in court, it's definitely impossible to tell what piece of what goes where after it becomes a LLM token, and also impossible to tell what future lawsuits will decide about it.
Where does that leave OpenAI? With the good ol' "I grabbed something off the internet because I could". Why does that sound familiar? It's something people have been doing since the internet was invented, it's commonly referred to as "piracy". But it's supposed to be wrong and illegal. Well either it's wrong and illegal for everybody or the other way around.