I think for junior engineers, being in person is invaluable a few times a week just having a whiteboard around. Early in my career having a senior dev around to bounce questions off of, or work CTF problems together really, really helped me.
Certainly there is some number of managers who just want control over people, but i think that's probably smaller than what some commenters are implying. The The questions i use for if a particular way of working is a ruse or effective is this:
1. What industry am I working in? If you work in an industry physically making things, you're likely to also benefit from being in the office some days. Same with creative work.
2. What's the ratio of "senior" to mid and junior level employees?
3. Is the company willing to let individual teams make more flexible decisions? I.e go down to 1 day a week, 1 day a sprint etc?
My end goal is to understand the nature of the organization I work for, why it makes decisions the way it does, and if leadership wants to send a message, or if they are open to trying to find the way that is productive and keeps people happy.