The point is that you can calculate a conservative input power value of the entire circuit, including the 1 Ohm brown resistor and the reactor, with the information that we have. And in determining the COP of the system, it is the conservative input power value that is used.
This is only true if the measured volatge, 100mV, is the voltage across both resistor and reactor. So to be abel to calculate the conservative input power value with the information we have from the report we must assume that the report is wrong about what voltage is measured.
Since the report say "In the left in the figure there is two voltmeters that measure the mV of the current passing through the 1 Ohm brown resistance" not through the 1 ohm brown resitance and the reactor.