"anymouse, the "original" post specifically focuses the concept of closed position on the feet. Disregarding Polished/serendipidy/Quickstep's customary vagueness, I don't think that it is unreasonable to assume that she means "together" or "not separated.""
The original post did not specify a body part at all. When we finally got one specified, it turned out to be the distance between the partner's knees:
"The fault is because you know you are going into a Link the step gets taken too far to the left making it almost impossible to do a Link corectly, consiquently the step becomes open and the knees too far apart"
What is being described as needed here is in fact a promenade position of the feet, but one where the feet are close enough together that the knees can be nearly touching.
If you can actually have your knees touching while in the promenade foot position the book requests at the end of the progressive link, or only have them close, is an interesting question.
But there can be no room for argument that, however close you wish to have your knees there, the book still defines this as a promenade position.