I've never met anyone who claimed "fluent in sarcasm" as a trait who could pick up on other people's sarcasm or jokes.  You could say "why did the chicken cross the road," and they'd say "huh?  Was there a chicken on the street?"  Most of them aren't terribly sarcastic themselves either.  It's either just repeating jokes from memes or tv shows, or saying rude things then going "oh my god I was joking!"