What is the difference between "hamstring tendon" and "common hamstring tendon"?
In the paper you cite, they are talking about the tendon on the other side from the ones you've listed, at the "origin from the ischial tuberosity" (quoted from the abstract).

In this case, the word "common" is used in the dictionary sense of "same" rather than "ordinary": it's "common" because it's the same origin for the different muscles that make up the hamstrings. This terminology is used elsewhere in anatomy, too, for example the common carotid artery splits into the internal carotid and external carotid; the "common" portion is the larger proximal vessel.