The difference between Anthropic and a cluster bomb supplier is that cluster bomb manufacturing in the United States requires permits. The government is only going to give them to companies that are working with the United States and its allies, which means that company has zero leverage to make requirements (e.g. "don't use them on humans.")

Separately, as a note to your made up example:

Cluster bombs are uniquely efficient against humans, especially in trenches. The US is not a signatory to the international treaty banning their use. It does not like being limited in how it conducts war. I strongly doubt that it would agree to terms from a private enterprise to similar effect.