Monday and Friday are clearly because people have been clocking in late on Mondays/early out on Fridays. They're the people you want to be annoyed with, because if that's a regular thing, it's pretty obvious.
I think a lot of offices are calling people in. Dh's is just doing a "consultation" and they're expecting to be told 2 days a week in the office. There are a few issues.
Firstly, there aren't actually enough desks for everyone, by quite a long factor (moved offices during covid) and so it's going to have to be formalised when people are in, which is what's causing an issue. A lot of people do do around 1-2 days a week in, but it's round when other people are in so they can meet in person. Dh is working currently on 3 projects, but there are others working on far more, so coordinating on that isn't going to be easy.
Secondly they're pretty niche. So since wfh has become a thing, they've found recruitment far easier. They have people employed who are 2hrs+ away who come in perhaps once a month. One in his team lives way further and what he does is every couple of months stays in a local hotel and has a week in.
These people will probably resign if they have to come in twice a week, for obvious reasons.
So they're hoping they're going to be told on average 2 days a week in the office, but with flexibility, including for those employed during wfh to have less.
Dd started working in a mostly wfh place, and it would have been far easier for her at the beginning to have people around to give her the little unofficial bits of information. They took a long time to pick up. When there was a new starter last year she went into the office every day for a fortnight to help them as she remembered how hard it was - and she vastly prefers wfh.
I also wonder about loneliness. Dh has weeks when he is totally wfh and he sees the family, and goes to church. That's all he does with "real" people. People who haven't got a lot of social things on may get more and more isolated, and that isn't good.
So I can see both sides.