The wording is very sensationalist. It’s currently hard to trace any single output specifically, but that doesn’t mean we don’t know how it works. The algorithm and theory behind it are very well understood. It’s just that the algorithm is very complex (and uses very large amounts of data), which is what makes tracing a single response token by token so hard.

When you read something about how we don’t understand how AI works, you can safely skip that article, they intentionally use dishonest language to make it sound like something mystical is going on.