The acid in the oil may be true in theory but the amount after running it for a few minutes after the oil change would be absolutely minor.

The only part is agree with is NOT starting it up while in storage. Idling will not get the oil hot enough to get rid of the moisture.

As for all the other ways to do the end of season change. I'm sure nobody will have any problems. Nobody is going to ruin their engine by doing some other method, we are just sharing the best way to do it.