The Mishna lists the parshiyos that were read by the king. Rashi is bothered how the king is able to skip from one parsha to another, since we said in the mishna that we don't skip unless you will be able to roll to the destination point before the translator finishes? Rashi answers that the king didn't have a translator so he was able to skip. The Rashash wonders why this halacha isn't mentioned in shulchan aruch (that with out a translator you can make people wait), but it seems completely counter intuitive! If there is no translator one should not be allowed to skip at all?
I found that the Meiri (right before 32b) asks this question -
והדברים מתמיהים שאם כן אף בפחות משיעור זה אסור
The Meiri offers another approach that it is not considered g'nai for the tzibur for anything which is a kavod for the king. This idea is explained by Tosafos 41b that a king can only be mochel on his kavod for mitzvos that are a direct kavod Hashem, but for a mitzvah that is kavod for a human being, a king cannot be mochel because the requirement to honor a king takes precedence over any other mitzvah of kavod. Here too, the kavod that the tzibur has to have for the king out weighs the kavod hatzibur that the king is supposed to have for them. See also Tosafos Yom Tov.
But, What is the peshat in rashi, it seems to make no sense?!
Perhaps Rashi holds that the genai to the tzibur is that the translator is going to make them wait, but the reader making them wait is not a problem. The rationale is that the reader is like the mouthpiece of Hashem reading for the public. Any waiting caused by the reader is considered waiting for Hashem to continue speaking kaviyachol and therefore not a g'nai. But if there is a translator who stops translating, and then the tzibur has to wait, that is a g'nai for the tzibur. This is meduyak in rashi 40b d.h. v'ach - ולא יגלל ס"ת לשם מפני שהוא רחוק ויש שהות שיפסיק מתרגם, וישתוק לפניהם ואין מתחיל בפסוק אחר ואיכא גנאי - Rashi is speaking about the translator, that his silence is causing the tzibur to wait and that is the g'nai.