Why do many of the pros hold the cue in the palm of their bridge hand, then roll their wrist into an open bridge when approaching the shot. Orcollo, Chang, DeLuna, Kaci, etc
Took a quick look at CJL and it looks to me like he's checking/cleaning the shaft. Chalk debris etc... with the glove any dust will tend to stay on the palm side. Haven't looked at the other players but I'd guess similar.
First guy I seen do that was Keith Mcreedy. IIRC When he wasn't running around the table, he'd sometimes, chalk up and brush the chalk out past the ferrule with his loop bridge. Only saw him a couple times but quite a memorable experience.