Yapp shared with me this was part of event-specific rules for the PLP this year.You see this in a minor way when players clean the cue ball while they are preparing to break. Typically they spin it against the cushion. In a refereed match, the ref normally cleans the cue ball and If there is a ref around, I think he should be the only one who cleans the cue ball, even between racks.
See "Unsportsmanlike Conduct" #2 and #3.