The voluntary resignations are what they are--I can't fault anyone for taking a good deal, and from what I have heard (married to someone in the government, with many friends as well) no one is being pressured inappropriately.
However, the other cuts are dominantly people who are 'probationary' which means that they are new to their positions, either by being recently hired or in some cases promoted. These people are, actually, on the whole harder workers than those who have been in their jobs for a long time, because they're still being competitive in order to move forward. The non-probationary employees have stronger civil service protections which means that they are harder to fire. This is the major discriminant used to decide who leaves and who goes.
Per the article, the 10% includes both people that have taken the deferred resignation offer and probationary employees. The former are probably generally older staff that are already considering retirement. The latter are, according to what I could find on the definition of federal probationary employees, either new hires or existing employees that were promoted or otherwise moved into a new position.
I don't see how you square that with "the bottom 10% of the NASA workforce". On the back end you're losing institutional knowledge. On front end you're losing your future contributors (see the old adage about "eating your seed corn").
How do you expect anyone willing to work four you in the future if you treat people like this...
One episode of Suits comes to mind.
Let’s be honest, firing people reduces cost, because humans are expensive, and executive and ownership class want to keep costs down and profits up. That’s it.
Framing the narrative in terms of firing the worst performing employees puts the blame on individuals.
In a health company, of course if you can’t perform the duties of the job you should be helped to get to that point (if employer is nice) and let go if you eventually can’t. A firing of 100s of 1000s of people at once is a failure from the top in terms of planning.
Which is likely the goal anyway.