I had a client do something similar but it was 2 weeks, and short enough that the entire company did go on one “wellness/reset” break. Their attrition rate slowed to nearly zero and eNPS scores skyrocketed. People really needed the mental break.
I also worked for a company that did this annually over the holidays, again for 2-2.5 entire weeks-- no work. period. This is an organization that also experienced very little turnover.
I will say that 4 weeks seems like something is not being said about any work continuing behind the scenes. “nearly the entire company” can mean many things, and I bet those in excluded are a group of people that may need it the most. Pure speculation of course!