"Benetton and Compiani acknowledge financial support from Ripple’s University Blockchain Research Initiative."
Ripple is a competing blockchain that doesn't use PoW. I'd say that the paper was funded to make Bitcoin look bad. It even starts off with two quotes that are not relevant. Further down in the article it even declares Ripple as a 'top crypto' among BTC/ETH, which in reality, while it does have a large mcap, it is orders of magnitude smaller than BTC/ETH.
There was certainly some issues with the residential and small time miners in upstate new york. Most of that got banned, pretty quickly, in 2018 (5 years ago!).
The larger miners, who took over the old smelters, and the ones drawing the most amount of power (by a lot), are definitely getting their feeds directly from the dam and those feeds were not being used once the smelters had shut down back in 2014.
Why not look at other states that have a huge amount of hydro mining, like WA? They focused on, literally, one portion of one state. Is that enough of a data point?
Another good tidbit... those dams actually need a constant draw of power to remain in service. Bitcoin is helping with that and providing a source of revenue that went away when the smelters shut down.