That can;t sork -- if the *fan* is allowed to wobble (the cowling will wobble with it and, inevitably, dig into the ceiling).
I installed a fan above in-laws kitchen table ~35 years ago and the hanger was a hook-and-eye; hook went through center knockout of octagonal box into 2x6 straddling ceiling joists. Lift eye on fan stem onto hook. Connect wires. Slide cowling up fan stem until *close* to ceiling. Secure set screw.
The two fans on the back porch (here) use special brackets with a "ball" end on fan stem that slips *into* saddle bracket secured to Jbox (special boxes with reinforced bosses that transfer load directly to back/top surface of Jbox). They have far less wiggle room as the fan motor assemblies are much wider, shrouded and very close to ceiling -- I can't even see where the cowling *would* fit against the ceiling (no ceiling on porch)