This lengthy article by a self-described "AI enthusiast" muddies the waters. Yes, Anthropic has capacity constraints, which is why they rented Colossus from Musk despite the danger of being distilled.

The real reason is that the hype around Mythos has already gone quiet because it does not find more than other models. That is, nothing at all in most open source projects. If you hide the model, embarrassing statistics will not be posted.