The Malbim points out that in the wording of Haman’s letter, Haman had left out the detail that the attack would occur in every state so that the governors would not know yet that he planned to have a mass genocide. Haman did not want them to know that other governors received the same orders. Thinking their orders were unique, the governors would focus on the work at hand, and not be unnecessarily concerned and overwhelmed regarding the success of the operation.
In Ma’aseh Chemed, the Steipler Gaon writes that the letters do not explicitly name the Jews’ enemies in contrast to Haman’s letter (Esther 3:13). There, Haman was concerned that some people might misinterpret his decree to target some other disliked minority. Therefore, he spelled out clearly who the enemies were. By being specific, the ring-leaders could start making plans, stockpiling weapons, collecting Jewish addresses, etc. However, by performing these acts, the Jews’ enemies made themselves conspicuous to the Jews. For this reason, the purported enemies in this verse could be vague because Jews knew exactly who they were already. How complete and precise is H-Shem’s justice! Haman and his cohorts dug their own graves.