No, I seriously doubt he was putting it on, he was definitely slurring and such, sure people can fake that, but I think he was on some kind of serious downers.
Joaquin had a clef lip/palette— perhaps he has a bridge and didn’t put it in for the show— who knows. It’s sad if he’s on drugs— it’s so common for people who lose a family member who’s on drugs to start doing drugs themselves in order to get close to them in some weird way.
He ruled as Johnny Cash. Compare that to the abysmal lip-synching performance of Johnathan Rhys-Meyers as Elvis. Of course it was smart to use Elvis’ real masters, but Rhys-Meyers DID NOT look like he was singing it at all.