...I mean, all I have to go on is my own experience and what I've seen from the workers around me, but your claim doesn't line up with that data at all. For instance, my team just lost three (out of 8) of its most talented and most productive developers (including our lead developer) who quit over corporate policy changes, including WFH changes. Obviously, to reiterate, this is a small sample size and sampling bias, but... it certainly doesn't support your claim.
EDIT Sorry, I misread your comment. I fail to see how "only the productive people are quitting" supports "therefore, fire as many unproductive people as you can". Doesn't that just leave you with... zero people?
Your claim supports your parent's claim -- that the productive employees are the ones quitting, and the unproductive ones are those who are not quitting.
You try and scare the unproductive people into being more productive.
And you try and scare the productive people into staying by implying that the market may not be all that hot outside. Or whatever. Scare tactics don't exactly rely on rational thinking.
Also, you are reclaiming the work being done by the fired. That work can be reassigned to the people not fired. And hopefully, those people will be too busy to quit.
EDIT Sorry, I misread your comment. I fail to see how "only the productive people are quitting" supports "therefore, fire as many unproductive people as you can". Doesn't that just leave you with... zero people?