I'm a bit confused, how is it redundant here? It's trying to make the best possible argument from one side that seems to be wrong. Instead of taking the argument at face value, it takes the most charitable understanding of it (not requiring that it happened before, but some parts where perhaps inspired during later revisions) and tries to argue that case.

'strongest “steel-man” case' is the same thing as strongest case; “steel-man” adds nothing.

The question I asked was intentionally trying to see if GPT would go for it or just give me the answer it thought I wanted, but it did a pretty decent job at not just saying “you’re absolutely right” etc. Myself I don’t believe there to be much influence between the two.