Yes, it would be helpful. For instance, a classical Class A amplifier presents the impedance looking back into the collector output resistor (more or less) when it is off. It duplicates the input signal, with varying degrees of accuracy, but out-of-phase. So does out-of-phase matter to you? Is this (for instance) an AC or a DC waveform? If it's AC, you don't care if it inverts, most likely- if it's DC, however, it is totally useless for this purpose.
Both of these, of course, assume that the signal of interest is an analog signal. But if the signal is digital, you don't care about the waveform- just when its on and when its off.
Please tell us more about your application.