Its true and unfortunate. Typescript is the new Coffeescript. It splits the ecosystem. Flow is a progressive enhancement and improves the ecosystem. Typescript has had more push in the mindshare marketing from Microsoft.
With Flow you don't even have to opt-in to a new syntax. You can just use comments:
function foo(val /* : boolean */) /* : string */ {}
Using really powerful inference you can also write much fewer types. If you have well types libraries [you sometimes don't need types in your code at all](https://medium.com/@thejameskyle/flow-mapping-an-object-373d...).So you use a opt-in comment-based syntax instead of a opt-in non-comment based one for type-annotations.
Hardly a big difference.
> Using really powerful inference you can also write much fewer types
I'm just going to assume you didn't know typescript does this too.
Typescript is nice. You should give it a try once. You may end up surprised:)
Doesn't TypeScript actually predate all of those tools? So that logic doesn't seem reasonable.