We've made some changes here for the next release.
Specifically, the following polyfills are no longer included through some composer-fu :
We'll continue to exclude polyfills that come in through other packages dependencies, though this will always be based on the XF minimum requirements. This means polyfill libraries may still come in, e.g. polyfill-php72 is still going to be included even if you're using PHP 7.2 or above.