The poster to which I responded and the article are each speculating on the "why" for this contract. That said, we do not need to speculate about Cybertruck sales - Business Insider reported that Tesla sold only 5,400 of them in 2025Q3.
We know from this that they do not need the same level of third-party 4680 capacity, and (call it speculative if you so desire) this is the most parsimonious explanation for the L&F write down.