Importing without extensions is not a TypeScript thing at all. Node introduced it at the beginning and then stopped when implementing ESM. Being strict is a feature.

What's true is that they "support TS" but require .ts extensions, which was never even allowed until Node added "TS support". That part is insane.

TS only ever accepted .js and officially rejected support for .ts appearing in imports. Then came Node and strong-armed them into it.