You guys are probably right about Pentangeli actually being the boss in New York.

But like Lilo says, everyone knows that Michael was in fact still the one pulling the strings.

So that's why I said my 'interpretation' of this is that Pentangeli was defacto Michael's underboss.

His official title was that he was a caporegime. I don't think it was FFC's intention to let us think the chart was just assumed by the FBI. I don't think it's that complicated. That chart was made for us as viewers to understand the Corleone hierarchy, and ofcourse to give a sense of authenticity regarding that scene.