That 20 FPS mechanical shutter in the 1DX III is either just there to show off (D6 only does 14 FPS, A9 II only 10) or to give people a reason to try out mirrorless.
But how slow is their mirrorless mode... 10.5 FPS. That's weird to me, why not put your best mirrorless tech into your flagship DSLR so people can at least try out if it does something for them without using a mirrorless right away. The thing costs a lot anyway.
Anyway, the specs look like they pulled a Canon. But they also went with the same new type of AF sensor that uses image sensors instead of simple line pairs. I wonder who had they idea originally, and who's execution is better. My bets are on Canon, AF using pixels has been their thing all the way back since the introduction of DPAF.