This is almost certainly ahead of layoffs. This allows them to reset already accrued PTO to 0, and then when the layoffs start to occur after January 16, they won't pay out that PTO (since, again, it is 0).

To give a specific example: Imagine someone has 30-days PTO as of January 15. If they were laid off the company might be contractually obligated to pay it out at whatever rate was agreed (e.g. 50% @ 200K salary is $8K, 100% is $16K). But as of January 16 with the flick of a pen they have 0 PTO and saved thousands or even millions of dollars in layoff costs.

I don't mean this disrespectfully, but people who are "pro" this move are naive. Research has shown this reduces PTO taken and regardless it reduces the cost of layoffs/takes money out of employee's pockets.