I wouldn’t be surprised, especially by this point in his long career, if Pitt fully understands that comedy is mostly not where his talents reside, leading him to take roles that are a bit lighter than usual for him, but still don’t require comedic powerhouse performances.
It was nice of Greenberg to add that he feels like Brad Pitt has, though, in fact been funny on screen since his failed Cheers audition.
While Pitt is, by no means, considered a comedic actor at this point, he has been in a few movies that are lighter in tone than his usual fare, and he’s managed to elicit some laughs in films like Snatch, the Ocean’s Eleven franchise and (in what is probably his looniest role to date) Burn After Reading.