Well, not quite -- the post was saying that if you never interact with the other party again, regardless of whether they're playing hardball or softball, there is no post-agreement fallout if you play hardball, because, well, there is no post-agreement interaction (like the buying a car example).

Presumably, for a job or professional services contract, where there is significant post-agreement interaction, the article's prescription for and reasoning behind not playing hardball still applies, even if the other party plays hardball.