2.2. Redirection

In some cases, the server may choose to respond indirectly to the
QUERY request by redirecting the user agent to a different URI (see
Section 15.4 of [HTTP]). The semantics of the redirect response do
not differ from other methods.

For instance, a 303 (See Other, Section 15.4.4 of [HTTP]) response
would indicate that the Location field identifies an alternate URI
from which the results can be retrieved using a GET request (this use
case is also covered by the use of the Location response field in a
2xx response).

No, that is incorrect. In a 303 response, the Location field identifies
a replacement target resource that will perform the same query when it
receives a GET request. To complete processing of the original QUERY, the
user agent will need to perform a GET request on the resource referenced
by Location. This allows the original query to be identified for reuse as
a normal resource and for the results to be cached.