I am overall responsible for the team that produces and figures out developer productivity metrics for Google.
I can assure you there is lots and lots of real data on this, so there isn't a lot of need for random supposition based on people's desires (WFH vs not) and biases. There are too many comments in this thread to read every single one, but most suppositions i read seemed just to reflect biases and personal preferences rather than any real data.
It's IMHO a little odd to see people assume that any really successful tech company is not going to be able to figure out and succeed at maintaining whatever overall level of productivity they want (IE pre-covid, pre-covid-50%, pre-covid+50%). The ability to adapt and be productive/effective in changing conditions is often one of the things that makes companies successful in the first place.
The thing that is much harder to fix is stuff like personal well being.