No surprises...
"... engineers who joined prior to the pandemic and worked in the classic office setup were performing better than remote workers..."
... because these workers are used to interacting: in an office environment you can have the ad-hoc conversation in the kitchen that leads to a new approach or a problem being solved, you can see if the person you need is free to talk (does anyone actually pay any attention to those status indicators of messaging apps?) or if someone want to talk to you, you can guage if the new joiner is struggling with their setup or a team member needs a hand...
Of course, there were always the few who would just sit there with their headphones on, ignoring everyone, trying to pretend that the rest of the world did not exist and acting like interacting with other team/department members were an unneccesary distraction - the "not a team player" types, probably the same ones who are making the "if I'm forced back into the office, I'm leaving" noises now.
Individuals may be as or more productive at home than when in the office. But teams as a whole? It's debatable. I personally have seen days lost because someone "was productive" for the entire time but did not realise that they were working from out-of-date information or an incorrect approach, resulting in work having to be re-done.
Managers - as much as thse of us at the coal face like to moan about them - have the over-arching view; they can see that while individuals are being productive, teams are often not performing as well as they did pre-covid due to this lack of ad-hoc communication. So it's natural they want us back in the office (although I would not be at all surprised if some of them had other motives). And it's likely that companies that do get people back in the office, even only for a couple of days per week, will start to accelerate: not only will their teams' communication have returned to full capacity, but the refuseniks who would rather stay at home and not interact with their team on anything but a scheduled basis will have left.
And should this come to pass, the companies still trying to run fully remotely will most likely see that they are being out-competed and possibly be force to adopt the same policy.
I know I'm going to get downvoted to hell, but I'd wager that in another 5-10 years time, we will all be back in the office at least once per week.