It's a mandate. They could have mandated that remote work is acceptable. They didn't. They are now surprised that people are leaving.
Just like how if you don't like the mandates issued by your government, you are free to move to a different country. Or to petition it to change them. They are still mandates, though, despite you choosing out of your own free will to submit to them, by virtue of not leaving.
This website also has mandates about how its posters are expected to behave, that you submit to - despite being here voluntarily.
I'm a citizen of the country I was born in, which I did not choose. I can leave the country physically, but that itself doesn't invalidate my citizenship, or my obligation to pay taxes.
You choose the company you work for, and you can leave at any time, and you don't owe them a thing.
Just like how if you don't like the mandates issued by your government, you are free to move to a different country. Or to petition it to change them. They are still mandates, though, despite you choosing out of your own free will to submit to them, by virtue of not leaving.
This website also has mandates about how its posters are expected to behave, that you submit to - despite being here voluntarily.