If you are testing on a single machine, this file will get cached in your browser first. Therefore, subsequent reloads will return the browser’s version, which will not reflect Cloudflare having minified the file at the edge.
You may need to load the file again in an incognito window, or alternatively, do a hard refresh (typically shift + refresh) in the browser. Please note that it may sometimes take several seconds or longer for the file to become minified at the edge.
This is only an issue for each time you publish. Once published, after the first time a user loads the file, the edge will create a minified cached copy to serve to all subsequent users until your next publish.