And this 3 days in the office business won't work well either. If not everyone on the team picks the same 3 days to be in office, then what are you gaining? How would it make sense if there's barely any overlap among team members?

I don't think these companies have thought this through. Logically, the 3 days a week in office will slowly become 2, then 1. Or maybe teams will decide to only get together 3 days a month or something like that.

At that point, you're effectively fully virtual anyway.

These companies need to just dive right in, because the suggested format smells of poorly thought out compromise.