Rogue Dragon's teeth BUG in Iskar

This guy’s item was 741 but there were [shadows of the destroyer] and [fury of the destroyer] in his buffs. Could you tell me how he did it?
The logs’ link:https://www.warcraftlogs.com/reports/JBKRmyZhzPLapFrA#fight=27&type=auras&source=10&translate=true

Seems like easy. He just needs to change weapon in battle.