Did you read to the end? The point of the paper is not the gotcha about which planet is really closest. Their point is that their PCM method allows you to quick

Did you read to the end? The point of the paper is not the gotcha about which planet is really closest. Their point is that their PCM method allows you to quickly estimate distances between groups of planetary bodies in a novel way. They aren't trying to be "gotcha" about it, they're introducing a new model for estimating solar distances.