I don't know why you're being downvoted. You're exactly right - there are a few tiny divergences between ES6 and TypeScript. In particular, try compiling some classes with Babel's strict compatibility mode and compare the output to TypeScript's output. There are several small semantic differences.

Also, there a few constructs in TypeScript that generate JavaScript code, like enum and module.

THAT SAID, TypeScript is basically ES6 + type annotations, and can certainly be used as such.