This is actually what matters. Energy spent and not hash power as so many take as main metric of how secure bitcoin network is. Hash power keep increasing because better and better ASIC miners gets built. But if energy put into securing Bitcoin network stays same that means that no matter how high hash power will go the network i same secure. The main problem is what also is said in the tweet. These numbers are just his estimations. It is much easier find a hash power number then to calculate energy spent.  Actually even better metric would be money spent to pay electricity spent for mining. Perfect but even harder to get metric.