The managers will bring it up because they have pressure on them coming from higher up to have their reports all be compliant with the work-from-office policy, and in extreme cases, they would be expected to manage out the people who are flouting it. Not doing these things could easily result in an unsatisfactory performance rating for the manager.
Yes, a job (not the job) of a manager is to gain trust up and down. Imagine, just for a fleeting moment, that "communicating and explaining corporate policies" may actually play a role in this! "Here is why we have to RTO 5 days a week: [corporate bs]."
Now let's also imagine that you already have the trust of your direct reports (I would think a lot of Amazon managers don't but that's neither here nor there). You explain a policy to them - they have to be in the office 5 days a week or Things happen, whatever they may be. This person just refuses to do it. Is the manager to just say "oh well I don't want to 'be a dictator' so I'll just let them ignore this policy?" Of course not. They'd be abdicating part of their job if they did that.
yes the manager at that point decides if it’s worth burning the trust they’ve built or if they should push back harder.
see in the example you’ve given, you’ve still placed the employee second over the business. or to put it another way, a human over money. so poof, gone is the trust if you did have any.
Completely ignoring any RTO/WFH-specific aspects, one of the jobs of a manager is to communicate and explain corporate policies to their direct reports, and enforce those policies.