This matters for senior management only, i.e. those who make decisions. This doesn't matter for middle management (even though they act as if they are senior managers) and that's completely irrelevant for line workers who don't need to "read body language" to get their linear work done.
Line engineers totally need to read body language. Presenting a paper or design? You need to read when your audience is drifting. Discussing a contentious code review? Body language can tell you loads about how much they are committed to their approach. Mentoring other engineers? Running an ops review? Asking for approval for something?
There's a million scenarios where understanding body language makes you a more successful line engineer.
Another great reason I want to continue working remote: Why would I want to leak any information in my body language to coworkers or management?
I have no idea what they are going to do with said information, and the fact that I'm not already saying whatever it is my body language is communicating means that I would not like to supply it.
Umm what? Based on my 15+ year experience in tech sector (similar for my partner), my take is that in-person interaction is absolutely necessary for the middle management layer (though certainly not sufficient). They need to interact with both the bosses and the trench soldiers. If everything else is held constant (same org, same talent, same level, same effort), an in-office middle manager will absolutely outperform a similar person in a remote setup.
I'd go even one step further and say that in-person interaction is critical not only for middle managers but also for those individual contributors who want to jump to management or tech-lead positions.
