It appears that's not the case.
The four-time Pro Bowler interfered in the Andre the Giant Memorial Battle Royal during the WrestleMania pre-show after an altercation with Jinder Mahal. As Mahal was attacking Mojo Rawley, a longtime friend of Gronkowski, he began taunting Gronk before throwing a drink in his face.
Gronkowski responded by hopping the barricade—not before a well-intentioned security guard could briefly get in the way—and then shoulder-trucking Mahal to the ground. Rawley would go on to win the battle royal and celebrate with Gronkowski in the ring.
A former University of Maryland defensive lineman, Rawley (real name Dean Muhtadi) was briefly signed by the Green Bay Packers and Arizona Cardinals but never made an NFL roster. He and Gronkowski became friends when Muhtadi played at Maryland.
Gronkowski was limited to eight games last season due to injury and underwent back surgery in the fall. By the looks of things, he should be back at full strength sooner than later.