There's no way 25% of their total employee base are "checked out". Yes, a bunch of folks close to retirement or fed up with working there will take the deal. But with the job market as it is, a whole lot will roll the dice on keeping their job through the inevitable follow-up round of layoffs.
This is just an optics-friendly way to soften the blow of 25% layoffs.
It is much better than optics friendly, because it gives the affected people a chance to determine their own destiny.
Layoffs absolutely suck, and there is likely more pain on the way, but if the alternatives are voluntary buyouts + layoffs vs plain layoffs, the first is much better.
In my experience it's more the case that 70% of employees are checked out