IMO the maximum current that the converter draws will go down as the supply voltage goes up. I don't think however that it's valid to assume a linear relationship for four reasons:
1) The PF may change as the voltage changes.
2) The converter efficiency may change as the voltage changes.
3) The converter might supply more output power as the voltage goes up.
4) The generator's waveform may change as the load requirement changes.
I think the only reasonable way to get at the answer for any converter-generator combination is actual test and measurement. IMO a PD converter is a good match with a Honda inverter generator because the converter doesn't supply full output power when the AC voltage sags, so as the generator nears its maximum output, the converter will to some degree back off on its power requirement.