I have no horse in this race but just wanted to point out the absurdity of this methodology:

“The generation data for wind, rooftop and utility solar data was rescaled to supply ~60%, 25% and 20% of demand respectively over the year. For example, over the last year utility solar generation has met 5% of demand. The target for utility solar was 20%, so I rescaled the last 7 days of utility solar data by 4x (ie, 20% divided by 5%).”

That's a perfectly sensible methodology, do you have a specific problem with it?

"Wind and Solar are fine as long as they're only X% of the grid, but you'd need <silly amount> of storage for lulls in wind and sun once they get close to 100%" is the question it's answering.

As the other commenter pointed out, that source is more absurd than your initial claim, but I didn't down vote your comment.

He threw shade on it but without a good reason as the reply to him points out.

Rescaling existing production is exactly how to demonstrate whether the peaks and lulls of solar and wind would sufficiently line up in a 100% solar/wind/pumped storage/hydrogen storage grid. Real data > hypothesized data.

What's absurd is the fossil fuel/nuclear lobby's "for public consumption" models that assume that the sun and wind both go out for 4 weeks at a time every winter and that the only way to store energy is with lithium batteries from 2012.