Players, teams, rosters, and contracts are generated from real data. Draft classes are included up to today.
There were only 11 teams in 1947, playing a very different brand of basketball than today. Live through expansion drafts, league rule changes, team relocations, economic growth, and changes in style of play.
Draft prospects always start the same, but they have different career arcs in every league. See busts meet their potentials, see injury-shortened careers play out in full, and see new combinations of players lead to dynasties.