Whether there was explicit information in the plates on this point, we have no way of knowing, but Mormon understands that this increase in hostility is not government-sanctioned punishment. Rather, individuals are pushing the limits of their treaty, restrained from actually killing them only by the treaty-oath. They manifest their desire to harm, not in military situations, but as individual harassments of slapping and overburdening. Either Mormon is interpreting the situation based on his reading, or his source spelled out the implications, which Mormon reports.
Given those two options, it seems more likely to me that Mormon is the interpreter. The actions of the Limhites suggest that they did not fully understand what motivated the attacks on them but to which they respond militarily.