Ok, so the modification was the "Here’s a good way to visualize what happened." explanation.
I would say that the whole (short) paragraph is intended to clarify why the answer to the question is "Yes; you should switch."
Maybe it was not a good way to visualize what happened after all. Experience shows that some readers were unable to understand the argument.
However, none of them complained about the explanation being wrong because those were two completely different problems (only in the second one the host will always avoid the door with the prize, apparently).
