Glancing through the study, I'm curious about both sample bias, and the lack of formal measurement. I'm not an expert in this type of thing, not even an amateur. I'm poking holes to see what's left.

"Participants were identified via media reports featuring Australian firms trialling the 100:80:100 model, in addition to companies listed on recruitment sites that specialise in 4DWW jobs. In other instances, eligible organisations were recommended by the participants themselves."

I'd expect organisations with positive results will be the ones recommended by other participants - "talk to these people, it worked for them too!"

I'm also interested in whether or not organisations converted all staff to 100:80:100, or if it was optional. Is the performance driven by peer pressure?

Finally, the participants' measures of productivity will have significant lag time in them, so it depends on trial's length, e.g. "revenue", "profit", "csat", "projects delivered on time", "net promoter score".

Table 1 has "Duration", but the units are unlabelled, if it's weeks, it's less than a year, months is probably better for seeing performance changes.

It's an interesting qualitative study, I'd certainly like a four day work week with no change in comp.