Haxe is much older than TS/Flow: it was created in 2006. It's "unsurprising" by design, but there are advanced topics, like pattern matching or macros (AST metaprogramming), and the fact that you're not limited to targeting JS.
It's not as cool (and backed by big Californian co) as JS/TS, but Haxe really grows on you when you start mastering it.
Let's be careful not to limit Haxe to OpenFL, which the linked article isn't even using.
The article points out that Haxe is a great option for creating portable application logic while the game is using Unity for rendering.
Other uses for Haxe are the JavaScript target which a number of companies are using extensively in the same way you would be using typescript/coffeescript.
