8 years ago my nephew emailed me from one of the zones. 1 hour before Obama showed up at his AO, they were stood in formation and read a long list of do's and don'ts. Don't boo. Don't make this statement or that statement. And they were basically ordered to clap if and when he made a speech. Attendance was mandatory, Article 15's for anyone not showing up or leaving early.
I bet no order had to be given for President Trump's appearance.