And, iirc, then they estimated total consumption from well-funded and very active mining pools. I.e. exactly the operators that you would expect to run the most efficient mining equipment. Meaning all you do is being overly optimistic, as in "we claim mining uses less energy than it actually does"
And, FWIW, the kind of methodology that was used to produce the Bitcoin energy consumption is the same kind of methodology that is used to produce statistics like GDP, inflation, employment--basically every macroeconomic indicator. If you're going to complain that you can't quantify Bitcoin's energy consumption, then to be intellectually honest, you need to complain that the true inflation rate or the true size of any country's economy is impossible to quantify as well.
But a factor of two wouldn't change any of the analysis! If the article said "60 TWh" instead, would that be any less horrifying? No, it wouldn't.
you don't know efficiency (watts to hash) of the equipment on a global scale
In other words, one person might use 1watt to produce 1hash. Someone else might use 2watts -> 1hash.
That would be literally half as efficient and muck up any quantifiable numbers on a global scale.
Never mind all of the other things I mentioned above.
The reason why this is always such a highly debated topic is literally because it is something impossible to quantify.