Jens, I think you're misunderstanding the purpose of the study. From the abstract:

"To this end, an extensive method for measuring the battery capacity of series produced electric vehicles (EVs) via the DC charge port was developed."

Remaining battery capacity of EVs is measured from internal electronics and is typically displayed on the vehicle's console. Some cars (Nissan LEAF, others) are equipped with a diagnostic port from which owners can retrieve a detailed analysis of the state of charge (SOC) and remaining capacity of each cell. For owners of fleet vehicles, measurement would require connecting to this port for each car in the fleet to be able to relay capacity data to a utility.

The author has discovered a way to make this information available from the charge port, so the utility would be able to determine how much capacity remained for the entire available fleet whem they are being charged. Connection to the diagnostic port is unnecessary, resulting in a significant savings of maintenance effort and expense. 

The repeated cycling of any electrochemical battery degrades capacity, whether it's charging by V2G or charging it every night. So yes - V2G will degrade battery capacity faster than if a vehicle's owner uses it for driving alone. Whether the owner worries about it or not, he can expect reduced battery life from helping his utility meet electrical demand - another casualty of attempting to power an electrical grid with unreliable, intermittent renewable energy.