The Valley is mostly tech, while SF is more the web shops. SF didn't even have much tech exposure at all until the dotcom boom; in 2000 it was still mostly old line industries (a stock exchange!) and music and other art. People in tech lived up there and commuted to work in the Valley.

I don’t have statistics. It’s in the name though, “silicon” valley. The South Bay is home to the semiconductor industry and its ecosystem.

My own company has about 15k employees in San Jose, and we’re all back to the office full time. Many of us can’t do our jobs from home, it’s hardware work.

The "Silicon" part of Silicon Valley is still very much relevant. Intel, AMD, nVidia, etc. all have major presences down there. There's also a multi-billion dollar industry supporting silicon design shops in various ways, and they're all in SV too.