Akamai keys its cache on the exact query string, so every phrasing of the same shopper intent becomes its own entry — and most are evicted from a shared LRU before they are ever reused. Harper sits behind it keyed on the reduced query, so the tail lands on the head.
Hit rate is the wrong unit for peak. During peak the question is whether search stays up, and that is a queueing question about an origin with a fixed number of render slots. Below is a simulation of that queue, run twice over identical traffic — once keyed the way a CDN keys it today, once keyed on the reduced query. Only the key differs.