Update: This path does exist, but it has changed. The point where it connects to Chemin des Usages is more to the north, and the shape of the path is different. The only evidence of the old path is a signpost in the middle of the bremble bushes. Sadly, the new path isn't visible on satellite and I'm not here for long enough to go back and find out the new shape. Requesting someone else take a look at this.
(warning: there are barking dogs in that building)