A straw man is a misrepresentation of someone’s position or argument that is easy to defeat: a “steel man” is an improvement of someone’s position or argument that is harder to defeat than their originally stated position or argument. ~https://wiki.lesswrong.com/wiki/Steel_man
I think people might assume steel-manning to be an altruistic cooperative effort to achieve harmony in dialogue. But it might also be that steel-manning can be used as a counter attack to a disingenuous opponent in a non-cooperative setting. If they say, “You don’t understand my argument, read it again” in response to our rebuttal but we feel we have already understood their argument (and made a logical counterpoint) we can then respond, “I will steel-man your argument”.
Then we put the argument back to them such that it will perfectly represent their thesis AND also in a palatable way.
They are forced to concede either that you DID understand their argument or they must concede their thesis.