Client Hints exposes JS equivalent of
navigator.connection APIs that help in loading optimizations. But other APIs like preload support detection (
DOMTokenListSupports(document.createElement("link").relList, "preload"); ) are also relevant to loading optimizations and can benefit from inclusion in Client Hints.
Example use case: In my server side rendered app, I render inline scripts. These scripts can have different contents based on if client supports preloading. I could add basic defer script loader if preload is not supported or a more sophisticated script loader if preload is supported, where script execution time is controlled by certain events.