Delaying scripts is a powerful technique to speed up the page rendering, but some scripts modifies the DOM, so you can't simply defer them.
With preprocess scripts, Swift Performance will run these scripts on server side, and cache the modified page, so the visitor don't need to wait until the script run in the browser and rendering the page.
Preprocessing scripts is the next level to optimize javascripts, and improve Web Vitals score for WordPress.
See more:
https://docs.swiftperformance.io/know...