Dan, just speculating here, but your incident could also be be caused by the "flow limiting device". There is an explanation on that with my #7 post link.
If you turned on the 2nd cylinder, and the furnace was still calling for propane, then the flow limiting device will not open fully. It needs back pressure to completely open. Somewhere between swapping cylinders, maybe the furnace shut down and was no longer calling for propane, the system had enough back pressure, and the flow limiting device fully opened. Even an open oven pilot light valve is enough to trigger the flow limiting device into not opening fully.
Of course, it could have been just as you said.....the tank was opened to fast allowing the OPD to shut off the flow on a full tank.......in that case my long winded explanation above is a moot point.
Ideally, the OPD should shut the gas off entirely, and only close when the tank gets full at filling. That is because once a pigtail is screwed onto the tank, the OPD valve should stay open, regardless. Of course, that is theoretical.
The flow limiting device will give a low flow situation if there is not proper back pressure.