Hi. The author of the article here.

The webpack and Rollup experiments were done with uglify and gzip enabled. The numbers are based on the reported values in Chrome when running the code here: http://www.syntaxsuccess.com/rollup-bundle http://www.syntaxsuccess.com/webpack-bundle http://www.syntaxsuccess.com/closure-bundle

The uglify code was accidentally commented out in the source on Github, but I have fixed that now.