Okay, let's get real - how many times per year, for the average cyclist, does the situation of having five or more cars backed up behind them on a narrow TWO LANE road actually happen, and how long does that usually last?
Riding solo, this might happen to me once a year, and rarely lasts long enough for me to start looking for a place to pull over. Either the drivers get an opportunity to pass in the next lane, or the road widens, or I am turning off the road. Or, traffic is slow anyway, and I'm just taking the lane with my speed limited by other traffic or signals ahead. I've pulled off the road three or four times in the last decade to disperse backed up traffic on a narrow two-lane. I do this voluntarily - there is no law requiring slow drivers to pull off the roadway in NC. Maybe I'm lucky that most of the busier roads have additional lanes for passing, and a lot of the two lane roads here are wide enough for same-lane passing.
Now consider large group rides. I see five or more cars backed up behind large groups fairly often. Are the vehicular cycling proponents arguing that dozens of cyclists riding together on a narrow rural 2-lane should leave the roadway to let five drivers pass? I suspect not. Here I think we need to consider the relative convenience of the cyclists and the motorists. The group ride leaders I've spoken with are more interested in making adjustments to formation, i.e. platooning smaller numbers of cyclists with gaps between platoons, so that motorists can pass more easily, rather than leaving the roadway.
So, please show me a specific quote where some vehicular cycling proponent is arguing in favor of an onerous burden to be placed on cyclists for the benefit of passing.