how would a cookie help with better auto-detection? to store the platform, maybe, but how do you determine whether the user wants a mobile/desktop version to begin with?
It doesn't help the detection, it means that the override when the detection fails is remembered so the site knows to just pick a particular version instead of using the detection method at all.
It is a work-around improving the UX on the second and subsequent requests, not a fix for the root cause.
