Well, boss of all bosses in my opinion doesn't necessarily mean that you control every single boss in this case. Luciano made sure there would be nobody who actually controlled every boss. But lucky was boss of all bosses. The title was still there but the definition was basically changed. But it means you are recognized as the most powerful boss. You are the most respected boss. No boss does anything in your territory without your blessing. I think the lucchese's and Genovese's would be more frightened of the repercussions of moving in on gambino territory than the Gambino's would be if they moved in on their territory. And I would take Phil Leonetti's word being that he was a high ranking member in the mob. I think he would know which family is the most powerful at that time.