private URI clientEndpoint(Request<?> request) {
        return request.getHandlerContext(HandlerContextKey.CLIENT_ENDPOINT);
    }
It should redirect signer if the request is CreateBucketRequest or ListRegionalBucketsRequest with outpostId present
aws-java-sdk-s3control/src/main/java/com/amazonaws/services/s3control/internal/handlers/EndpointHandler.java