Request times within a week are not uncommon for scheduling these types of interviews but I haven't encountered a situation where rescheduling was a problem. Examiners have schedules and time frames to get certain tasks done so maybe he was up against the clock.
Sending the informal questionnaire answers back might be helpful so you can keep the interview shorter but they should not tell you no if you want to do a verbal interview. From the FDIC exam manual "The EIC will contact the institution and arrange a PEP interview to be conducted either by telephone or through an in-person discussion."
The process is in the FDIC Exam manualhttps://www.fdic.gov/regulations/compliance/manual/2/ii-4.1.pdf