So, I tried it today. I called up, then asked for a standard briefing
and started giving the briefer the spiel. The guy actually interrupts
me a couple sentences in and asks incredulously if I'm getting a
briefing or filing a flight plan. When I tell him it's a briefing, he
takes a firm grasp of the call and converts it back to the
question/answer format.

Well, I'll try the great experiment again next time. These McMinnville
FSS guys seem, based on my super limited sample size, pretty committed
to that format.