Earlier quoted context omitted.
Probably because American AI companies are on the hook for quite a lot of investment money. I think they are trying to find the magical moat to justify their valuation. Revealing optimizations similar to these would pretty much reduce their competitive position.
Chinese labs are also still behind, so they’re incentivized to collaborate and have no reason to do it in private. I suspect their tune will change if they ever take the lead..
Even if they're ahead they don't have enough GPUs to scale. Open sourcing is hence a good strategy to at least get market share (even if not $).