As a current employee (thoughts are my own, blah blah) in my experience this has been the defacto operating posture across many MSFT engineering teams for some time. They are paying out carried over leave - which is nice.
It's not nice, it's a legal requirement and precisely why they're doing it. They almost certainly are looking to remove that financial liability going forward, and have the added benefit of having people on "unlimited" vacation take less vacation than those that otherwise earn it over time.
This announcement will at least make it more fair going forward to teams that sticked to the rules and did report the days off. The teams that didn't report still get an advantage in a larger payout though.
At the end of the day, for a salaried employee, it's not a vacation day if you do any work -- and checking email IS work -- no matter how it's accounted for, most Microsoft FTEs never truly take a vacation day. So it's all just a matter of accounting anyway.
Wow. Microsoft must not be a publicly traded company then. When I was managing teams my tracking of where time went, which you know, ended up being reported in financials was pretty important as fraud in publicly traded financial numbers is kinda a big deal. Not sure I would commit that level of fraud for 'good will' on my team, no matter how much I liked them or was trying to boost morale.