Exactly. "HDMI is the same" sans VPs. Meant they probably didn't want to leap frog to 4:2:2 10-bit. Maybe developing it for the a7S III or a9 II. We'll have to wait... If you've heard of anything feel free to share.
Never? You have to get out more. It's used during wartime. Basically, a go-to when you want the "Saving Private Ryan" look.
The "improved" video Sony is pointing out on the release is more about color space. They've added Hybrid-Gamma Log profile, Gamut3.Cine/S-Log3... improved dynamic range for color grading.
My guess, in terms of bit/sampling, they didn't want to jump the a9 (HDMI out 4:2:2 8-bit). We'll be able to tell more about alpha when the a7S III comes out.
Physical dimensions are the same as the a7R II but button feel has changed texturally. Viewfiinder same as a9.
Good overview video to watch:https://www.youtube.com/watch?v=HYG7_BXKsEM