The author asserts that we should see 5x GDP/c if we had 5x power usage per person and their own graph shows that that's not the case because it's a flawed assumption that ignores increases in efficiency and transitions away from energy intensive manufacturing to service based.
The best evidence for that is that the GDP/c didn't fall off when we fell off the HA curve. In fact I took the GDP per capita and Energy consumption per capita data from world data bank and the ratio between the per capita GDP vs the per capita energy consumption has been going up steadily since we stopped following the HA curve.
Between 1960 and 1970 the ratio between GDP and Energy Consumption per capita was essentially static at .74 then after 1970 the ratio begins to increase showing we're producing more per unit of consumed energy at a nearly linear rate. By 2014 which is the last year they had the Electric power per capita data the ratio was all the way up to 4.2. Eyeballing it the relationship is almost perfectly linear each year we get a little better at producing GDP for each kWh we consume.
I even redid the calculation based on raw energy use in kg oil equivalents and it gets even more drastic. 1960 to 1970 it goes from .53 to .69 GDP/kg oil equivalent [0]. Then after 1970 the rate increases quite distinctly going from .69 to 1.58 in 1980, 3.11 in 1990, 4.5 in 2000, and 6.79 in 2010.
It's pretty clear from the data that we're getting better at producing things with the same amount of energy. It's an assumption that simply making more power would increase the amount of things made.
Electricity use per capita: https://data.worldbank.org/indicator/EG.USE.ELEC.KH.PC?locat...
Energy use per capita in Kg oil equivalents: https://data.worldbank.org/indicator/EG.USE.PCAP.KG.OE?locat...
GDP per capita in current USD: https://data.worldbank.org/indicator/NY.GDP.PCAP.CD?location...
[0] nice.