It also depends on where you live. Where I live, if you are working a fully remote job, and your employment contract doesn’t specify that you need to work in the office, if they try to force you back into the office then you can quit and go on employment insurance since it would be considered a constructive dismissal.
I don’t think this is going to be just cutting fat though. They’re going to have their desperate and least-talented employees working in the office while their most talented employees will end up finding remote employment elsewhere. That’s how RTO always goes.