That polyfill relies on a third party which can then effectively gain analytics for your site. They store and keep the referring URLs and user agent combinations.
That polyfill relies on nothing since you can run your own custom 'polyfill' server, or just download the bundle and serve it from your website. It's completely open source.
https://github.com/Financial-Times/polyfill-service
You're complaining that a public CDN runs some analytics. But they all do that, and this project doesn't mandate that you use their CDN.