Physical scientists often use the term "root-mean-square" as a synonym for "standard deviation" when referring to the square root of the mean squared deviation of a signal from a given baseline. In our case, high values could be caused either by frequent path vector changes, unstable/congested links or a combination of both. Low values would naturally imply the opposite. Of course, there may be other interpretations too.
It can be argued that the RMS or standard deviation should not be used to describe the data considering the nature of the delay distributions.