From the report's summary:

61 organizations participated. A year after the pilot, 54 of these organizations continue to implement the 4 day workweek. Among these, 31 organizations have decided to make the 4 day workweek a permanent arrangement. This means 89% of the participating organizations have continued with the policy in some form, and within this group, 51% have committed to the policy permanently.

One thing that is missing is the effect on output - do productivity improvements offset reduced hours?

I would also like to see a comparison between reducing days worked and hours worked per day, which is rarely mentioned.