“Cache” means space used for disk caching. It’s free to be used for processes as needed, but the system consumes idle RAM until then to speed things up, so it’s technically not “free”, even though it isn’t used by system processes. In Linux, used - cache gives you the actual consumption by processes.

Orientation of hot vs neutral

It’s absolutely a grand plan, and they’ve even written it all down. It’s called project 2025, and it’s their carefully engineered play by play for exactly this and more.