I'll treat this as a genuine question. No, to "steelman" is to engage with the strongest possible version of your interlocuter'so argument, rather than the weakest. An especially effective steelman case will (genuinely!) strengthen or clarify the opposite point of view before laying out the case against it. It's a way of granting respect to those with whom you disagree, and (I find) a discipline that helps me avoid empty rhetoric.

But, yeah: if you find that the steelman version of the opposing argument won't be borne out in reality that's a promising line of attack. You'll argument will be more likely to be effective, however, than if you attack the strongest rather than the weakest ("strawman") version of the case.