Well, yeah. But if people who have enough privilege to take a stand against workplace exploitation do take a stand, that helps slow down the ongoing creep of how much they're allowed to dick you around at work.
Make no mistake, by "not allowed to work from home," this employer meant "you will not be paid for work you do at home," while clearly expecting the employee to do work (such as answering work emails and taking work calls) while at home. (If the employer didn't expect that, then they wouldn't have noticed when the worker stopped doing it.)
If you're expected to respond when the boss summons you outside of work hours, you are on-call. If you're on-call, you should be paid.
Expecting white-collar workers to be on-call for no extra pay is wage theft, no different from if a retail or food service employee is told to, "Clock out before you clean up/close out your station, so you don't go over your hours."