Well if Vito and Clemenza were dead, why would the government include them in their charts, or care 2 cents worth about them?
For movie purposes only as they were "known characters" to the viewer. If they weren't included people would then have asked why they weren't included.
My interpreration of the chart is that it was Michael's faction/Rocco's regime in Nevada. The Corleone family could never have only 30 made men. But to include like 250 members (which is what the most powerful family in the country would have) was ofcourse too much work for the makers of the film.
