I don't know if anyone is tracking it explicitly, but in more nuanced stories, (eg. Ben Thompson's stratechery[0] - paywalled), it does come up.
Basically, most of these tech companies have been hiring at a constant rate for years, and also experiencing constant attrition. Once the economy soured, and then hiring freezes started, attrition rates had crashed, and the employee count wasn't as affected by freeze as desired. The layoffs have been roughly a reset towards the headcount before the freeze for many companies.
While the whole article is paywalled, I'll quote an excerpt from ben Thompson:
> The popular narrative right now about these layoffs is that tech companies dramatically over-hired during the pandemic, but while that seems to have happened with Amazon — and for arguably very good reasons given the way that e-commerce shot up during lockdowns in particular — the reality is that the rest of the tech companies largely increased at the same rate they always had. Sure, the number of employees they added was large, but that was a function of keeping the same hiring rate off of an ever increasing base.
> In short, no one was giving up a job at one of the big five tech companies this year as fear spread about a broad-based slowdown in hiring... These companies, though, adjusted more slowly to the slower rate of attrition, which means they accidentally increased their headcount... the relatively limited size of the layoffs to date actually reflects that: these companies are not returning to their pre-pandemic levels of employees, but rather to where they would be had they kept up roughly the same rates of hiring this year that they have over the last ten
[0] https://stratechery.com/2023/tech-layoffs-big-techs-hiring-r...