Has everyone accepted that?

3/4 companies in the Bay Area senior software engineer interviews require a System Design interview where they will tell you "what if you had 10m users" and expect a distributed write-heavy sharding answer

You’re not wrong in the literal sense. But the “inside baseball” of that question is just that it’s a prompt to talk about how you would horizontally scale a system should the need arise. It’s not a prompt to start questioning whether 10mm or 200mm is the specific limit.

Well that's the thing. You don't need a NoSQL database to design a data tier that scales to accommodate distributed write-heavy workloads.

Lots of people were mad that my employer developed a new distributed NoSQL database engine, but it was literally just an API to encapsulate what an application doing "sharded MySQL" would do in its own data tier. A lot of this is a question of framing and storytelling.