By Daniel Chavkin The commisioner explained the league’s stance on the 20-year-old. When the Bruins signed Mitchell Miller, who was charged and convicted in an Ohio Juvenile Court for assaulting a classmate in eighth grade, the organization saw a large amount of backlash for the decision. General manager Don Sweeney acknowledged the risk in signing the player, but claimed the team did a vetting process. However, that didn’t involve checking in with the league. NHL commissioner Gary Bettman said he didn’t hear from Boston before the team signed Miller. “What I understand and have heard through …