What does "steelman" mean in this context?
A strawman argument is a weak argument to justify a position you disagree with; its purpose is rhetorical: It's meant to make your position look strong to onlookers (and perhaps to yourself).
A steelman argument is the strongest possible argument you can come up with to justify a position you disagree with; its meant to help you find the truth by taking seriously the people who disagree with you.
OP is using the word slightly differently than normal, in that the position OP disagrees with here is, "Docusign needs 7,400 employees". A strawman would be, "Docusign needs 7,400 employees because it needs to show the stock market that it's a serious company" -- weak and easy to demonstrate that it's stupid. A steelman would be, "Docusign actually needs that many sales people and customer service reps."
From the context, it might also mean "rebut this as strongly as possible", "criticize this" or "defuse this argument".
It's unfamiliar wording to me as well. Does anyone have a rough etymology of "steelman" as a verb?
A strawman is an imaginary opponent who is easy to defeat. Like a scarecrow (a human-like figure stuffed with straw, meant to scare off birds from crops) which would be easy to defeat because it doesn't fight back when attacked.
The connotation is the opposite of straw-man, so OP wants people to start from the assumption that it's true they need all those 7,400 employees, and explain why this would be the case. OP is not looking for cynical explanations such as that they only have so many employees due to incompetence.
What a grossly unnecessary word.