> It's not a polyfill though as it supports IE9+... A polyfill is support for old browsers that don't have native support.

And thus it is a polyfill indeed, since IE9 does not support HTML5 input types (and more generally HTML5 form extensions).

Polyfill != works back to the stone age, it just means providing backwards compatible functionality. Aside from that, there are some polyfills that aren't even technically possible, or would destroy performance, in older browsers

Do you not consider anything a polyfill if it doesn't support IE 1.0?