Good idea.
Specifically the input current and voltage curves over this period would allow the resistance of the heater at different temperatures to be calculated. While I know of no material that has such a dramatic fall 500->1250 and then a very slight (typical of metal) rise (1250-1400) if the resistance could be determined from the data that would be best.
While extrinsic (ie undoped) semiconductors exhibit dramatic decreasing resistance over a temp range as thermal energy knocks more carriers into the conduction band they do not fit the bill:
they have much higher resistivity than you'd need for this heater
they do not have this 1% increase until much higher temps than the region over which resistance decreases.
they have low conductivity at room temperature - so the heater could never get started.
here for resistivity of Si vs temperature. We expect a total resistance on order of 4 ohms (ball park figure, based on the comment about 40A + in the report).
Of course, if such a material existed (not Inconel) all that would be needed is for Rossi to state what he uses. I doubt that would happen - Rossi knows when absence of information serves his purposes better than giving information. So the answer has to be voltage and current, or power and current, values as the device warms up. They should have these since they have tracked power and current throughout the active tests.