It wasn’t a lucky shot, it was more trial and error. My test code is here if it helps, though I probably cleaned it up a bit after realizing I could just shift values instead of using multiplication and an offset. I adjusted the global brightness algorithm until I didn’t see stepping.
From memory, the APA102 data sheet uses 1/31 as the unit for fractional brightness, so following the data sheet you shouldn’t be able to set brightness to 1/2, 1/4, etc, but in practice you can. (Thats where there trial and error came in). Maybe the SK9822 actually uses the 1/31 fractions.