Not sure what relevancy a 2019 paper has today?

It also seems like they are constraining the system to have no overproduction.

It’s like assuming that a fossil based system has all its producers generating the expected capacity factor and then smoothing out the season and daily demand changes with storage. Due to the difference between summer and winter demand such a fossil system would also need to have months of storage to compensate.

Which of course is absolute stupidity. When you can just overbuild production capacity and leave a far simpler problem to solve.