People brazenly defy the RTO requests at my company. I suppose management could start turning the screws on people, but I have a feeling enough people are still willing to quit to make that impractical.
Where I work, they mandated RTO three days a week. It was largely ignored. Eventually they started checking badge-in access and strictly enforced the mandate.
There was a lot of grumbling about people quitting, but anecdotally I didn't notice much uptick in turnover at all. It's very hard to tell what will really make people quit. If the labor market hadn't softened a bit I'm sure we'd have seen more, but my guess is the disgruntled people weren't able to get full WFH without a salary decrease larger than they wanted to tolerate.