So it'd be a lot easier for him to just toss attacks from back there rather than getting up close and personal. But on paper it looks like that's going to hinder him far more than help him. Of course it makes sense, but like... What's he gonna do with that attack move pool now?
His only useful special move at this point is Shadow Ball, which is of course a great move for Ghost types, but the rest of his pool is full of helpful physical attacks. And it's not like his Attack stat was so good before that he can just keep using those moves, this boost in Special Attack may really hinder Mega Sableye's offensive capability. However, in retrospect, it obviously wasn't Game Freak's purpose to improve that side of Sableye's strategy, haha.