Good points based on your observations.I'm not an expert. Therefore can not dispute their claim...
However, I think the photographic "evidence" is a bit misleading. In the top photo is seems fairly obvious that there is NO tension on the chain at all - it is not even ON the right side gear....
I believe in the static state, either tensioner would make the chain taught.
Again, I am not disputing the claim of the original post... Just pointing out my observation of the photos.....