What They Saw
This nitrogenase was purified from Azotobacter vinelandii; they don't give details on culture conditions, so presumably it's the molybdenum version.
First, they observed that more ATP meant more hydrogen over time. The free phosphate-to-hydrogen ratio was similar at all levels though, so that makes sense. The same pattern was seen for nitrogen fixation, except the proportion of electron flux going to ammonia increased as ATP increased; more hydrogen was produced at lower ATP, relative to ammonia.
They found that whether under nitrogen or argon, the electron flux was the same; this was true over multiple ATP concentrations.