Hello,
I don't know if you noticed, but the article doesn't actually provide the code to do what they say.

What's more, Concrete5 5.7 already does that without any htaccess trick.

When developing your site's theme or blocks, you can explicitly load assets (js and css) by specifying whether they should be compressed and/or concatenated or not.

Look through the doc for registering an asset:http://www.concrete5.org/documentation/developers/5.7/assets/regist...

You will see at the bottom the options including minify and combine