Working from the office or the home is fine. They have both their strengths and you can build on them. Doing both, it's just suboptimal.
I have worked with this model, and it's the most frustrating thing having to go to the office, only to be stuck in Zoom calls, because some people are away.
It's important to understand that this study indicates that hybrid is better than full-time office. It isn't comparing hybrid to full-time remote.
So it's pretty obvious that remote work doesn't need to hurt productivity and employees prefer it because commuting sucks.
Interestingly, since the trial randomized based on birthday one would expect that individual clusters (4-6 people) were often split such that two days a week the cluster should be considered fully remote. That is, about half the cluster was at home so everybody would need to communicate in a remote-friendly way on those days.
Working from the office or the home is fine. They have both their strengths and you can build on them. Doing both, it's just suboptimal.
I have worked with this model, and it's the most frustrating thing having to go to the office, only to be stuck in Zoom calls, because some people are away.