A skilled carpenter can spit out a fight of stairs in a day or so. An unskilled one can spit them out in half the time. They're not nearly as complicated as you'd think.
This is still fake as fuck, construction projects are contract labor. They'll bring in the tradies they need as they need them and then fire the ones they don't, generally getting rid of too many people too early, rather than keeping people around they don't need.
Carpenters on these projects are generally finish carpenters, they'd be installing drywall and trim, and would be quite busy trying to keep up with the schedule.