In the prison scene with Kaladin, Wit does reference the fact that he is already using another world´s magic system in Roshar. While tuning his instrument he says something along the lines of: Perfect Pitch makes this all so much easier than it once was. Hoid in Warbreaker plays a critical part that would likely not be possible without him having reached the the third heightening. The comment just goes over Kaladin´s head. I suspect he does drop comments like that pretty consistently, but nobody cares because he is such an oddball.
