I would guess unnecessary delays. Leases or property ownership can be verified with a phone call but probably needs to happen during business hours and if you are prepared everything will have a better chance to go smoothly. Property ownership is public record but a lease might be a bit more trouble to verify if the landlord is privacy conscious.
Unless you're trying to prove a point, having everything they might want will make the process easier. If you want to get into an argument about what you are "required" to show, you may well prevail, but it may cost you six hours.