The wire resistance is different, these are different circuits, and the ESC may well be doing different things because of the change in PSU impedance it sees.
0.257 ohms is unacceptably high resistance in an RC motor setup, these motors pull dozens of amps. I suspect you are seeing the unintended consequence of the ESC having to handle its supply voltage droop many volts during the high current pulses, and adapting its behaviour in response.
You are also sampling a waveform with the ADC at a particular rate - unless that rate is more than twice the highest frequency in the waveform, the results are potentially bogus as you miss details.
When measuring a current signal that's got high frequency components like the pulse train going to an ESC you need to be careful about sampling artifacts like this - different measuring equipment will respond differently if its not able to handle the bandwidth.