Next-token prediction is just the training objective. I could describe your reply to me as “next-word prediction” too, since the words necessarily come out one after another. But that framing is trivial. It tells you what the system is being optimized to do, not how it actually does it.

Model training can be summed up as 'This what you have to do (objective), figure it out. Well here's a little skeleton that might help you out (architecture)'.

We spend millions of dollars and months training these frontier models precisely because the training process figures out numerous things we don't know or understand. Every day, Large Language Models, in service of their reply, in service of 'predicting the next token', perform sophisticated internal procedures far more complex than anything any human has come up with or possesses knowledge of. So for someone to say that they 'know how the models work under the hood', well it's all very silly.