Usman made contact with Yadong, appeared to pull back from a spinning elbow, and interfered with medical staff trying to reach Umar, raising the risk of a wider brawl.
Weidman said cornermen cannot be allowed into the octagon during post-fight chaos, even while acknowledging Usman was reacting to seeing his brother knocked unconscious.
The incident was Usman's second such breach at a UFC event after he jumped into the cage at UFC 302 in 2024 following Islam Makhachev's win over Dustin Poirier.