What will you do about ghost jobs? For example I see Microsoft has a bunch of generic software engineer roles listed, despite them just doing huge layoffs. If they were actually hiring they could have easily shifted existing workers into those. These aren't highly specialized roles.
I've never heard of a company doing a layoff in the way you describe, eliminating thousands of roles and immediately moving those people into open roles throughout the company. It assumes the employees are fungible and will be a good fit for any open position and would lead to everyone knowing the layoff is coming well before its announced.