Yes, I am sure that's what Dick was referring too. However, I would be surprised if today's practice is any different to my day. Surely these fancy flight planning programs on iPad/tablet make it very simple to submit a plan?
Obviously, there are occasions when an in-flight diversion would not have a chance to plan and that can usually be accommodated. But to blast off on a flight crossing controlled airspace without submitting a flight plan is going to cause increased workload for the controller.