I caught that too, Sonny. The original novel clearly states that Michael and Paulie were once classmates. That's why Michael felt bad when he heard what happened to Paulie. Falco's novel has Michael being four years older than Paulie.

Here's how I feel in a nutshell: Falco's novel was well written, but it was poorly researched. It's one thing to make an anachronism like the needle on the Empire State Building, but to get the ages wrong on major characters is quite another thing. And I still can't get past the Rosato brothers being portrayed as contemporaries of Vito's. They were clearly much younger than Pentangeli in Part II.