Does the audio signal in the time domain change much after a RMS from one person to another?
In short, yes. 

One thing that you'll find is that the human ear is actually relatively insensitive to phase, so you can take an audio sample, apply an allpass filter that doesn't affect the signal's magnitude spectrum but distorts its phase, and it won't make it sound much different to you. However, the time-domain waveform could look completely different. I'm not sure what techniques the researchers used in the link you gave, but I would guess that it isn't likely to be based upon the time-domain structure of the audio waveforms.