Earlier quoted context omitted.
My issue with it is even more fundamental than this: it is structurally impossible for Proof of Work to become more efficient. If you find a more energy-efficient way to mine, the correct decision is not to reduce your energy usage, but rather to use the same amount of energy to compute more hashes.
By computing more hashes, you raise the difficulty for everyone else mining so you do ultimately push out the less efficient miners.
However, this does nothing for the overall energy efficiency of Bitcoin, which could be defined as transactions processed per gigawatt. If energy gets cheaper, that number only gets smaller.