There is often an apparent overlapping step when linking figures together into combinations.
Different dance associations/societies have taken different approaches to describing this in their technique books.
The ISTD makes frequent use of the idea that the last step of one figure becomes the first step of the next figure.
Their technique for the progressive chasse consists of five steps and ends with LF back for lady. In most cases this LF back becomes the first step of the following figure, typically a natural turn of some kind, and the dancer mentally removes the overlap. However the overlap does not happen when following with a quick open reverse which just follows normally.
Other associations, most notably the IDTA, take the view that overlapping steps can be confusing so they have removed the final, potential overlap step from the technique of most of their figures, leaving the progressive chasse with just four steps that you are familiar with. This works well for most situations but, as you mention, when following with a quick open reverse an additional step is required. I do not think there is a specific name for this step. I generally just refer to it as a "walk".
Finally, just to confuse things even more, in the UK the NATD have recently revised their technique and removed overlapping steps to align more with the IDTA approach. Unfortunately they decided to add the missing link step onto the front of the quick open reverse. This makes them unique, AFAIK, in defining a quick open reverse starting the with man's right foot.
