The link between reservoir filling and moderate earthquakes has been very strongly established and accepted in the geological community.
What's unique about this is the size of the earthquake being linked to reservoirs.
Do these earthquakes from reservoir filling occur deep in the earth, or near the surface. If they only happen near the surface, and only at the time of the filling, it only suggests that the terrain around the reservoir is reacting to the water pressure. Kind of like a plastic bag expanding when filled with water.
All kinds of construction activity will set of instruments, with vibration...but we are talking about a massive quake from deep within the earth.