Which makes sense to me. In office is very much useful for collaboration, team building, etc. But you aren't doing that 5 days a week anyway.
My hunch is that team-building and the more social aspects need far less than justifies anything like once a week; and collaboration is always best done at point of need, not to a schedule, in my experience. That need might be week-long! That can happen! But to assume everyone's best served by some arbitrary ratio is patently absurd; so much so that I find it hard to take arguments for it in good faith.
I will acknowledge that new starters and juniors do need hand-holding, and in most companies that's hard to substitute out. The mechanisms for doing that face to face are well established. But I don't think that's impossible to migrate to a mostly remote experience.
Seems like a massive time waste for no benefit. I go to the office 1-2x a week and that's enough for me to meet my team members and collaborate. But any more than that is too much!
For my team we picked Mondays, so we can have our chats and meetings then and focus on work the rest of the week.