That's not true.
> If a company fires 100 employees and certain operations stop functioning, they may hire back 10 employees and reassess
How likely is it that 10 employees come back? How likely is it that critical institutional knowledge is lost forever?
> The result is a company that functions just as effectively as before but with fewer employees
Does it? Have you ever been through a reorg or restructuring at work? Do things ever get back to just as effective as before any time soon?
> This is an optimization of resources and efficiency
It's squandering human capitol, knowledge and reduced efficiency both in the short term and long term. It's the most expensive way to reduce your overhead. A far cry from optimization.