From that interview:
"We’re still using a magnesium alloy body, but the way the parts are combined makes it more rigid. I’m sure you’d like to know about the sealing, and that’s totally different to the previous models. Compared to previous cameras, the a7S III and A1 have a totally new body structure. I can’t give you details, but we’re using very advanced [sealing] technology with the Alpha 7S III and the Alpha 1."
"We had to develop a new sensor, and we implemented our latest imaging processor as well as a totally new analog to digital conversion method. That’s how we achieved high resolution and high speed. I cannot give you any additional details, I’m sorry!"
"We’ve evolved our autofocus functions, but we still think there’s room to improve. We will continue to strengthen our current technologies, but also will also [continue to develop] object and scene recognition - that will be key."