I spent some time at the agency Level Studios doing work for Apple. My role was to help maintain apple.com. In my time there I did work on the Apple Music and Final Cut portions of the site.
Though I believe it’s now changed, at the time, Apple was using an in-house custom framework that constructed pages out of Markdown and merged the output with stand-alone JS and SCSS files that were using in-house libraries to build each part of the site.
Main page that I worked on for the Final Cut section - built the JavaScript and CSS
Also helped a lot with this section of the Apple Music section of the site back in 2017.
https://web.archive.org/web/20171102003157/https://www.apple.com/apple-music/
https://web.archive.org/web/20221122181606/https://www.apple.com/final-cut-pro/specs/