Cynic in my wonders if they finally have an 8k display they are ready to sell then.
The previous Macs supported so many 5k/8k display at once, they arguably should be able to drive a single 8k display, technically.
Example, Mac Studio supports up to 4 x 6k displays AND 1 4k at once.
So that is 4 x 18M pixels + 8M pixels = 80M pixels
8k displays are 32M pixels, so Mac Studio is arguably already able to push 2x that many pixels...
Or maybe it's related to the HDMI chipset they chose specifically until now.