One reason I believe apple still uses temporal dithering is due to this tweet (from Rene Ritchie):
XDR Display: It’s a 10-bit pipeline to an 8-bit panel, but uses temporal/spatial dithering and other ‘tricks’ to output 1 billion colors in a way that’s virtual indistinguishable Terrific HDR, very little blooming, manual refresh settings for PAL/SEACAM, references modes!