It's not based on metrics for how well we actually do our jobs. It's not based on any study. It's not based on a comparison of individual contributors during work from home vs working in the office.
Let's just call it what it is.
Return to Office is management failure.
It's management unable to adjust past the 18th Century mentality of "If I can't see you, you must not be working." And while that might have been needed in a Victorian counting house 200 years ago, such an attitude is not needed today.
Management has to actually do their jobs and manage when their employees are remote, and they just don't want to do that. They don't want to work harder.
That really is the bottom line. Return to Office is not evidence based. It's feelings based. And that is why no argument will sway them. They didn't reason their way into this feeling, they won't reason their way out of it.