I'm not claiming that they do, but just to play the Devil's advocate:

Anthropic controls the full serving stack, so it can change precision, hardware, kernels and settings whenever it likes. Reducing the KV cache precision, for example, saves a lot of memory (and money). It may even be possible to quantise the model on-the-fly when loading it into memory. They don't necessarily have to upload a whole new model.

Even if they can't do the same on all platforms, we can't deterministically compare them anyway.