This style of cue bids, developed by the Italian Blue team, has now become the norm amongst tournament players. Below the level of 4NT, you treat first- and second- round controls equally.
West’s 4♦ shows first- or second- round control in diamonds (ace, void, king or singleton) and denies first- or second- round control in clubs. East, if lacking first- or second- round control of clubs knows immediately that a slam is not a good proposition.