Unfortunately that's not how the other 20% works. Cleaning up the grid and eliminating wasteful energy are both important things to do but don't always overlap in terms of outcomes.

When dealing with grids with lots of renewable energy, that first 80% is the easiest because you aren't nearly as concerned with seasonal variations in availability.

Eliminating waste doesnt change the fact that you might see a week or more of clouds and low winds in the winter making it hard (not impossible, but exponentially more expensive) to close the gap.

And eliminating wasteful energy use in times of relative excess availability doesnt change the fact that you may still need to power your fridge or a heater in the winter.