LogFAQs > #950103297

He certainly isn't referencing any criteria from the BEP or the treasury. The treasury has this to say:

"The law prohibits portraits of living persons from appearing on Government Securities. Therefore, the portraits on our currency notes are of deceased persons whose places in history the American people know well.
The basic face and back designs of all denominations of our paper currency in circulation today were selected in 1928, although they were modified to improve security against counterfeiting starting in 1996. A committee appointed to study such matters made those choices. The only exception is the reverse design of the one-dollar bill. Unfortunately, however, our records do not suggest why certain Presidents and statesmen were chosen for specific denominations."

So all they need to be are deceased important historical figures the populace knows well, which Tubman obviously is. You can piss in the wind all you want about who did more historically, but whats the point? You could always say certain people did more, but that would also include people who aren't on money who were more important than those on our money(for example, Salmon P. Chase on the now defunct 10,000 dollar bill...not really a household name in US history).