The description of agency here feels very “Lesswrongy”, i don’t think that’s how most people would describe agency. I think what happened is that people got used to “robust agency” and it also changed their concept of “agency”.
When people usually talk about agency i don’t think they mean that in some game theoretic / decision theory sense. It’s about taking initiative, acting with intention, etc.
But that’s the nature of identity: a claim that’s part of identity won’t suffer insinuations that it needs any arguments behind it, let alone the existence of arguments against. Within one’s identity, labels are absolutely superior to arguments. So the disagreement is more about epistemic role of identity, not about object level claims or arguments.