I'm not aware that Microsoft has a "return-to-office" mandate. Maybe that's only for some employees? I know quite a few people on product teams who are 100% remote.
They reportedly have an RTO mandate for all employees. Managers can override the mandate, and can withdraw their approval forcing them back to the RTO mandate default.
I expect driving senior talent away is part of the strategy - the senior talent demands the highest compensation, which is what these employers are combatting industry-wide and in coordination. They want to hire them back at lower wages later on.
If we read the article instead of just the headline, we see that it makes clear that Microsoft has a hybrid arrangement, and that said hybrid arrangement has still resulted in a loss of employees.
>Microsoft, which also enacted a hybrid RTO approach, saw a decline of 5 percentage points.