macsforme I plan to post my findings soon
The results of my investigation into temporal dithering on Intel-based macOS are as follows. This testing pertained to external outputs only (not built-in laptop displays) given that a capture card was used. The machines tested included a 2009 Mac Pro, 2015 15-inch Retina MacBook Pro (iGPU only and iGPU/AMD dGPU variants), 2012 13-inch MacBook Pro (non-Retina), and 2009 15-inch MacBook Pro. The GPUs tested in the Mac Pro included the original NVIDIA GT 120, an NVIDIA GTX 640, an NVIDIA GTX TITAN (Kepler), an NVIDIA GTX 1080 FE, and an AMD Radeon Pro WX 5100.
Notably, the macOS version and firmware version of each machine did not appear to make any difference in the outcome, in the cases where several were tested. Most of the HDMI output testing was done with a standard HDMI cable, but I repeated several of the tests with a high-speed HDMI cable, and it seemed to make no difference on my hardware.
2009 Mac Pro - All NVIDIA cards do have temporal dithering on DisplayPort outputs, and do not have temporal dithering on HDMI outputs. The AMD WX 5100 has temporal dithering on its DisplayPort outputs (which is the only type of output), but only when plugged in at boot time (not after hot-plugging the monitor). Having multiple monitors plugged in and hot-plugging them seemed to cause inconsistent results as far as dithering.
2009 MacBook Pro & 2012 MacBook Pro - The former has an NVIDIA dGPU while the latter has an Intel iGPU; on mini-DisplayPort outputs, no temporal dithering was detected.
2015 15-inch Retina MacBook Pro - The iGPU-only model (MacBookPro11,4) does not exhibit temporal dithering on either mini-DisplayPort nor HDMI outputs. The model with the AMD dGPU (MacBookPro11,5) does exhibit temporal dithering on both mini-DisplayPort and HDMI outputs.