The statistical review of World Energy that they source the data from does do the substitution method. And it knows that plant efficiency is increasing over ti

The statistical review of World Energy that they source the data from does do the substitution method. And it knows that plant efficiency is increasing over time so it updates the compensation factor it uses. That means that over time a nuclear plant producing the exact same amount of electricity every year will look like a declining primary energy usage. The effect is slightly muted by their use of a global average efficiency conversion factor. An actual country deploying globe leading efficiency fossil fuel plants would see a greater effect in the direct, un-substituted numbers as less fossil fuels will be needed to generate the same amount of electricity.