After news broke out about IOI being tardy to a university event and being replaced by senior group Epik High for the first act of the show, YMC Entertainment has released an official statement to explain the actual occurrence of events.
On May 13, YMC Entertainment stated, "The arrival time that the event coordinator asked of us was 10:30 PM KST. IOI arrived at the site earlier than this given time, and went on stage after accepting the coordinators' requests to host a photo time with the university students."
The coordinators of the event also added on the matter, "If IOI had been late, we would have filed a report ourselves. They were not tardy, and because there was a delay in the process of preparing for the stage due to the large number of members, Epik High took to the stage first after agreement between the two teams."
That cleared it up for us!