Overhired has nothing to do with the talent pool and just means they hired more than they actually needed or wanted, if the talent pool is large enough then everyone can overhire

Of course the judgement about whether people overhired is subjective on a per-company basis. My point is, you can't hire people who don't exist, and the ways to get people into the industry are limited. All other things equal, we would expect massive overhiring to be matched with very low unemployment in the industry, and the correction should not go below some baseline.