Even past the TLS point (CDNs terminate TLS, so they can read the body) there's a harder problem nobody's solved: to cache a QUERY the cache has to fold the body into the cache key, and there's no standard way to canonicalize a request body. {"a":1,"b":2} and {"b":2,"a":1} are the same query and two different cache entries; whitespace, float formatting, unordered keys all fork the key. GET gets this for free because the URL is already a normalized string. So "cacheable in principle" is real, but "actually cached" needs every layer to agree on a canonical form first - the same coordination problem that killed GET-with-body. I want QUERY for the honest semantics; I just wouldn't budget for cache hits yet

I think the simple approach of using a bitwise comparison will result in satisfactory caching for most applications.