Flow has built in support for the Language Server Protocol. tsserver doesn't even support LSP. I agree ts has better IDE support but that's in part because they don't use LSP. odd they expect others to follow it when they don't.
LSP is kinda irrelevant to the argument that they feel that TS+VSCode is geared towards real-world productivity, vs the feeling that Flow prioritizes academic goals over devexp.
1) For displaying to the user
2) Generating a CSS class or something to that effect
In both of these cases the above is quite a reasonable behavior, and will never cause a runtime exception, and very rarely even a business-logic error. But if I'm working with the result of a .find() or a maybe-property on an object type, I now have to add null checks (or at best || '' fallbacks) everywhere, muddling up my code and making it harder to follow.