No, not exactly.
It is a pure research ranking.
The calculation of rank has no dependence on post grad programs. In fact, many of the ranked institutions are banks and think tanks, not educational institutions. It also includes educational institutions that do not have Phd programs or do not have masters or Phd programs.
Amherst does not rank highly even when compared to other LACs that do not have graduate programs. Among NESCAC schools, Amherst’s closest research “peer” is Trinity,