Why do you think so? It's certainly capable of producing outputs along these lines if you tell it that this is what you want:
https://i.imgur.com/B2cHXRA.jpg
To me this implies that things such as "sarcasm" is a pattern simple enough for an AI to match - and that should go both ways, whether it's being generated or recognized.
If you're arguing that it won't be able to detect the more subtle sarcasm, then yeah, sure. But, well, Poe's Law predates GPT.