By "JSDoc is TypeScript", culi means "JSDoc syntax and TypeScript syntax are two alternative ways to describe types to the TypeScript compiler/language services, and the two syntaxes have nearly-identical expressive power".

I understood it that way too. Only that it fails in that interpretation.

Just because currently the most popular method for parsing JSDoc utilizes TypeScript-related tooling doesn't mean we should associate them with each other.

To my previous example, an ISO C++ can be compiled by GCC but also can be compiled by Clang (and many other compilers).