I don't believe that. For one thing, a huge proportion of people have simply never heard of Swift's essay; for another, it's quite possible to use the phrase in earnest even if you have. It's not as if ever since Swift it has had only his meaning.

But, sure, maybe he didn't mean for it to be taken totally seriously. Maybe he just meant that to 60%. Or 90.

(TL;DR: Prove that.)