Let’s be clear, this is not about “security”.
Manhattan has been a no-fly zone for non-emergency helos since before 9/11.
This IS about keeping the news choppers from getting an aerial view of the lukewarm attendance for her re-re-re-relaunch.
I think what you said, plus this: without the no-fly zone a plane would have been hired to fly in circles above the event towing a banner that read BENGHAZI: Never forget! Hillary fears planes towing banners and will likely try to have a no-fly zone declared every time she has an outdoor rally, even if she has to drag her ex-president husband to her events in order to get the no-fly declaration.