It is one of the most common complaints after a remodel or a new build: the house was handed over immaculate, and a week later every horizontal surface has a fine grey film on it again. Homeowners assume the final clean was rushed. Usually it wasn't. The problem is that drywall dust does not settle on the schedule a single clean assumes.
Sanded drywall compound produces particles small enough to stay airborne for hours, and the HVAC system pulls them into ducts, returns, and filters while the work is happening. After the crews leave, that reservoir keeps releasing dust every time the system cycles on. Clean once, and you have cleaned the surfaces, not the source.
This is why post-construction cleaning is done in passes rather than in one sweep. The rough clean removes debris, packaging, and heavy dust so there is something to work with. The detail pass covers trim, cabinetry, vents, tracks, glass, and fixtures by hand, with floors done last. Then, ideally after the system has run for a day or two, a final polish catches what settled out in between.
A few specific places account for most of the dust that reappears: the tops of door frames and cabinets, window tracks, the inside lips of light fixtures, HVAC vent covers and returns, and the gaps around baseboards. All are out of sight, all hold a surprising amount, and all release it slowly.
If you are a homeowner scheduling a final clean, do it after the last trade has left, not between them, and replace the HVAC filter afterward. If you are a builder, book the final clean around your inspection date and budget for the follow-up polish. It costs less than the callback you get when the client walks in on day eight.