The article describes a way to use custom XML stylesheets for sitemaps generated by Yoast SEO plugin. Custom stylesheets can be good if you want to get rid of spammy links back to Yoast website in every generated sitemap file.
Yesterday I made a terrible mistake by updating Yoast SEO plugin to its latest version (8.3) without prior testing. This resulted in significant server load. Luckily, the fix was easy.