Pretty much this. Google, Amazon, and other big companies are overrated

You can find a lot of interesting with outside of them. Even better, innovative work is being done right now by a company you never heard about before

AFAICT no one actually believes this. There are plenty of places where building something important will get you in the door for an interview. There don't appear to be any employers that would be satisfied by track record without whiteboard performance.

I think that is correct, that most employers today insist on the monkey show interview process. I meant it more as countering what OP said about feeling like garbage. Being a great engineer in fact (building reliable and durable systems) is at best correlated and at worst completely orthogonal to what is measured in interviews today.

When did this become a thing, and is it mostly an SV phenomenon?

I've never in my life (nearly 30 years in salaried dev/tech positions) had to do whiteboard coding in a job interview.