This is a clever trick (probably too clever) for setting up Eleventy to manage asset pipelines like SCSS and JavaScript transformations, as well as using hashes in filenames for cache busting.
I like to use NPM scripts for my asset pipeline instead of using Eleventy to generate assets and orchestrate everything. The latest release of Eleventy Dev Server makes that approach both easy to implement and quite performant.
Configuring Web Fonts in 11ty with Global Data | Aleksandr Hovhannisyan
Rather than using static font-face declarations for web fonts, you can take advantage of global data in 11ty to create a single source of truth for fonts and reuse those values throughout your templates and CSS.